Need some clarification on how to measure "field of view right"

[ars4l4n]

I drew a picture of how I measured the angle for "field of view right" and where the building obstructing the view is.

The building obstructs the view between 103° and 180° when measured from the left.
But since you say I should enter the angle measured from the center, does that mean I should pretend as if the 90° on my triangle were actually 0° and count upwards from that? That would mean the angle I need to enter as "field of view right" would be 13°, right?

[basbruss]

That is correct

[ars4l4n]

That is correct

Thanks. Oh and was it correct that I measured from the exact center of the window? Meaning, I put the spot with the number 0 on my triangle at 55cm, while the total window length was 110cm.