But the 150 cm knee wall height in your drawing is about 50 cm in the room. Right at the wall, the knee wall height is given as 125 cm.
No. The dimension, like the other one, is directly at the exterior wall.
In general, from my point of view, there is no clear and universally valid definition of how the knee wall should be measured. However, the drawing is unambiguous, and therefore there is nothing to misunderstand.
According to the drawing, it has:
-1.25 m knee wall, measured between the top of the raw ceiling and the bottom of the finished ceiling, i.e. 1.38 m after screed, or about 1.35 m in the "finished room" with flooring
-1.50 m knee wall, measured between the top of the raw ceiling and the bottom of the rafters
There is also the variant of measuring the knee wall between the raw ceiling and the top edge of the rafters, then the knee wall would be even smaller.