One relationship under test: the transom bar’s width against the light’s. Third row is the two real worst cases — 18px reversed in the primary button, and 16px in a browser tab.
The panes sit inside a transom frame; the bar is exactly as wide as the frame, so it is a glazing member, not a base.
The round-3 F1 geometry with the bar narrowed to the light’s own width.
Bar narrower than the frame — reads as the head of the door below.
The full doorcase read, upright element included.