If I “Reposition New Cards…” and I select the “Shift position of existing cards” option, then all cards whose due number was at or above the “Start Position” are shifted upwards by number of cards selected × “Step”. However, since cards of the same note end up with the due number using the reposition tool, it makes more sense to shift the other cards upwards by the number of notes selected × “Step”. It think it would make even more sense to shift the other cards upwards by ((number of notes selected - 1) × “Step”) + 1.
For example, if I have 5 cards of each note, and I reposition the five cards of the same note that are all at New #0 with Start position 10, Step 3, and “Shift position of existing cards” checked, then the 5 cards all become New #10, but what used to be New #10 now becomes New #25, New #11 becomes New #26, etc. I think it makes more sense for New #10 to become New #13, or even New #11.