question about the starter motor diagram

[mohammad]

In the provided diagram, the pinion gear is positioned to the left of the aperture in the starter motor where it engages with the ring gear. The functionality of the peculiar gap in the armature shaft remains unclear. It is presumed that the pinion gear must shift towards the right in order to engage with the motor's ring gear. However, if that is the case, how does the pinion gear mesh with the armature and occupy the gap in the shaft situated just below the ground symbol?

[foama]

I see the (above) picture as a symbolic diagram. Symbolic for the sake of explaining and understanding the principles. The actual starter looks different, but none the less works the same. The said gap in the middle of the rotating axle of the motor was drawn just for better understanding and ease of illustration.
The lever has a pin in the middle, not shown in the illustration. The lever is pulled by the plunger to the left in the drawing, and consequently the lower part of the lever moves to the right engaging the gear.