diff --git a/rpc/src/tests/fee_rate.rs b/rpc/src/tests/fee_rate.rs
index e4d41ebbef..e805334dc1 100644
--- a/rpc/src/tests/fee_rate.rs
+++ b/rpc/src/tests/fee_rate.rs
@@ -54,13 +54,12 @@ fn test_fee_rate_statics() {
             total_uncles_count: 0,
             verified: None,
 
-            // first element in txs_fees is belong to cellbase
-            txs_fees: vec![
-                Capacity::shannons(i * 1234),
-                Capacity::shannons(i * i * 100),
-            ],
-            // first element in cycles is belong to cellbase
-            cycles: Some(vec![0, i * 100]),
+            // txs_fees length is equal to block_ext.cycles length
+            // and txs_fees does not include cellbase
+            txs_fees: vec![Capacity::shannons(i * i * 100)],
+            // cycles does not include cellbase
+            cycles: Some(vec![i * 100]),
+            // txs_sizes length is equal to block_ext.txs_fees length + 1
             // first element in txs_sizes is belong to cellbase
             txs_sizes: Some(vec![i * 5678, i * 100]),
         };
diff --git a/rpc/src/util/fee_rate.rs b/rpc/src/util/fee_rate.rs
index 2cea14ba15..fbb1086001 100644
--- a/rpc/src/util/fee_rate.rs
+++ b/rpc/src/util/fee_rate.rs
@@ -83,20 +83,16 @@ where
         target = std::cmp::min(self.provider.max_target(), target);
 
         let mut fee_rates = self.provider.collect(target, |mut fee_rates, block_ext| {
-            if block_ext.txs_fees.len() > 1
-                && block_ext.cycles.is_some()
-                && block_ext.txs_sizes.is_some()
-            {
-                // block_ext.txs_fees, cycles, txs_sizes length is same
+            let txs_sizes = block_ext.txs_sizes.expect("expect txs_size's length >= 1");
+            if txs_sizes.len() > 1 && block_ext.cycles.is_some() && !block_ext.txs_fees.is_empty() {
+                // block_ext.txs_fees's length == block_ext.cycles's length
+                // block_ext.txs_fees's length + 1 == txs_sizes's length
                 for (fee, cycles, size) in itertools::izip!(
                     block_ext.txs_fees,
                     block_ext.cycles.expect("checked"),
-                    block_ext.txs_sizes.expect("checked")
-                )
-                // skip cellbase (first element in the Vec)
-                .skip(1)
-                {
-                    let weight = get_transaction_weight(size as usize, cycles);
+                    txs_sizes.iter().skip(1) // skip cellbase (first element in the Vec)
+                ) {
+                    let weight = get_transaction_weight(*size as usize, cycles);
                     if weight > 0 {
                         fee_rates.push(FeeRate::calculate(fee, weight).as_u64());
                     }
diff --git a/util/types/src/core/extras.rs b/util/types/src/core/extras.rs
index 4f401401c1..d02e4a8bb9 100644
--- a/util/types/src/core/extras.rs
+++ b/util/types/src/core/extras.rs
@@ -10,7 +10,15 @@ use std::fmt;
 use std::num::ParseIntError;
 use std::str::FromStr;
 
-/// TODO(doc): @quake
+/// Represents a block's additional information.
+///
+/// It is crucial to ensure that `txs_sizes` has one more element than `txs_fees`, and that `cycles` has the same length as `txs_fees`.
+///
+/// `BlockTxsVerifier::verify()` skips the first transaction (the cellbase) in the block. Therefore, `txs_sizes` must have a length equal to `txs_fees` length + 1.
+///
+/// Refer to: https://github.com/nervosnetwork/ckb/blob/44afc93cd88a1b52351831dce788d3023c52f37e/verification/contextual/src/contextual_block_verifier.rs#L455
+///
+/// Additionally, the `get_fee_rate_statistics` RPC function requires accurate `txs_sizes` and `txs_fees` data from `BlockExt`.
 #[derive(Clone, PartialEq, Default, Debug, Eq)]
 pub struct BlockExt {
     /// TODO(doc): @quake
@@ -21,11 +29,14 @@ pub struct BlockExt {
     pub total_uncles_count: u64,
     /// TODO(doc): @quake
     pub verified: Option<bool>,
-    /// TODO(doc): @quake
+    /// Transaction fees for each transaction except the cellbase.
+    /// The length of `txs_fees` is equal to the length of `cycles`.
     pub txs_fees: Vec<Capacity>,
-    /// block txs consumed cycles
+    /// Execution cycles for each transaction except the cellbase.
+    /// The length of `cycles` is equal to the length of `txs_fees`.
     pub cycles: Option<Vec<Cycle>>,
-    /// block txs serialized sizes
+    /// Sizes of each transaction including the cellbase.
+    /// The length of `txs_sizes` is `txs_fees` length + 1.
     pub txs_sizes: Option<Vec<u64>>,
 }