Oh I forgot: Both red lines are actually 10 degrees, BUT one is linear and the other is curved. In the scope field of view it is linear, in the bearing indicator it is curved due to being adapted to a full 360º circumference.
You can do an easy check: place the central vertical line on any fixed object (a tree). Take menthal note of where the linear 10 degree mark is now (Pick another tree as reference). Now move the scope to put on that second tree the central line: ou will see that the scope effectively rotated those 10 degrees
