It's description is a bit weird:

These bits select the number of pels that the video data is shifted to the left. PEL panning is available in both alphanumeric and graphics modes.

Apparently, this is true in 8 pixel wide modes(non-MDA). But according to the ET4000 programmer's reference manual, it's different?
It documents that, for 9 pixel wide modes, it's behaviour changes:
- 0-7: Shift 1-8 pixels instead(effectively +1)..
- 8: Shift nothing(so, effectively 0).
- 9+: Undocumented behaviour. (Does that mean: same as value 8?)

Is that the case for all EGA/VGA/SVGA adapters? Or is that just the ET4000?