C API - draw offset affecting drawrect twice?

I'm using playdate->graphics->setDrawOffset in the C API and I also have a custom drawing function for a sprite that I set with playdate->sprite->setDrawFunction. The function is receiving a PDRect called drawrect and according to the documentation 'drawRect is the current dirty rect being updated by the display list.' I printed out the values inside of it and it looked like for every pixel the drawrect is offset from the screens origin it is counting up and down by 2 pixels. Is there a reason for this?
If I have a sprite at x = 100 and drawoffset.x = 0 then drawrect.x = 100
However if I move the drawoffset.x += 1 then drawrect.x becomes 102 not 101.