Add troubleshooting info to Usage and Billing page

Turn the section on validating usage data into the intro paragraph for a
troubleshooting section. We don't actually need to compare the usage
reporting system to audit events, and removing the comparison makes this
information concise enough for an introductory paragraph.

Add H2s for issues we have identified with usage reporting and billing
on self-hosted clusters.

docs/pages/usage-billing.mdx

@@ -64,25 +64,6 @@ Set the `TELEPORT_REPORTING_HTTPS_PROXY` and `TELEPORT_REPORTING_HTTP_PROXY`
 environment variables to your proxy address. That will apply as the HTTP connect
 proxy setting overriding `HTTPS_PROXY` and `HTTP_PROXY` just for outbound usage reporting.
 
-### Validating usage reports
-
-The system that Teleport uses for submitting usage reports is independent of the
-system that Teleport uses for submitting audit events. 
-
-Teleport processes submit audit events to the Teleport Auth Service, which
-stores them on its audit event backend for retrieval by Teleport API clients. In
-contrast, usage reports are aggregated on a submission service that runs either
-on self-hosted Teleport infrastructure or Teleport Cloud, depending on the
-user's plan. The submission service persists usage reports in the case of a
-submission failure. After a successful submission, the submission service
-deletes the reports.
-
-It is not possible for Teleport users to independently validate usage event
-data, as there is no way to set up a third-party usage event destination or
-retrieve usage events from a Teleport backend. Reach out to
-[email protected] if you have questions about usage reporting on your
-Teleport account.
-
 ## Billing metrics
 
 Teleport uses the anonymized usage data described in the previous section to
@@ -144,6 +125,11 @@ to compute a daily TPR. Then we average the daily TPR over a monthly period,
 which starts on the subscription start date and ends on each monthly anniversary
 thereafter.
 
+If you recreate a single resource more than once an hour, this will affect the
+hourly average. For example, if were to create then delete 10 servers three
+times in one hour, Teleport would display 10 servers at any given time. However,
+for the entire hour, Teleport would report 30 protected servers.
+
 ## Usage measurement for billing
 
 We aggregate all counts of the billing metrics on a monthly basis starting on
@@ -155,3 +141,50 @@ Subscription, also known as a high water mark calculation.
 
 Reach out to [email protected] if you have questions about the
 commercial editions of Teleport.
+
+## Troubleshooting usage and billing
+
+Teleport aggregates usage reports on a submission service that runs either on
+self-hosted Teleport infrastructure or Teleport Cloud, depending on the user's
+plan. The submission service persists usage reports in the case of a submission
+failure, and deletes the reports after a successful submission. It is not
+possible to set up a third-party destination for usage events to independently
+verify usage event data. 
+
+If you are using Teleport Enterprise (Cloud), your usage data is accurate as
+long as Teleport-managed reporting infrastructure works as expected (check the
+[status page](https://status.teleport.sh/) for any incidents). On self-hosted
+Teleport Enterprise clusters, some conditions can interfere with data reporting.
+This section describes some scenarios that can lead to inaccurate data on
+self-hosted clusters.
+
+If you suspect that any of these scenarios describe your Teleport cluster, or
+your usage data appears inaccurate, reach out to [email protected].
+
+### Multiple Teleport clusters
+
+In versions older than v14.3.1, Teleport does not de-duplicate users as expected
+across multiple Teleport clusters that belong to the same account. If you are
+running multiple Teleport clusters with affected versions, the count of active
+users may be higher than expected.
+
+### Unexpected license differences
+
+When distributing copies of your Teleport Enterprise (Self-Hosted) license
+across Auth Service instances, you must not download a license multiple times
+from your Teleport account. Instead, you must download a license once and copy
+that license across Auth Service instances. Otherwise, the Teleport usage
+reporting infrastructure will identify multiple licenses and misrepresent your
+usage numbers.
+
+### SSO users
+
+In Teleport, single sign-on (SSO) users are
+[ephemeral](reference/user-types.mdx#temporary-users). Teleport deletes an SSO user
+when its session expires. To count the number of SSO users in your cluster, you
+can examine Teleport audit events for unique SSO users that have authenticated
+to Teleport during a given time period. The Teleport documentation includes
+[how-to guides](./admin-guides/management/export-audit-events/export-audit-events.mdx) for
+exporting audit events to common log management solutions so you can identify
+users that have authenticated using an SSO provider.
+