Two Types of Screwdriver Rotary Switch Dials Available
Figure 1. Images from the datasheet.
The A type seem to have a protruding shaft to take a knob. The arrow can be used when the knob is not present and as an assembly guide as to where to place the knob digit window.
The F type are flush.

No, this answer is not correct. Some of the A type are flat. I don't know.