Why is the grid slightly off when I import the audio after I matched the BPM of Pamela’s PRO Workout to my DAW’s?

You need to physically sync the two devices either via a MIDI clock connection or analogue style clock for the grids to match 100%.  Matching the displayed BPM readout across devices is simply not enough to keep them in sync due to slight differences in timing between equipment and the lack of a consistent starting point.

Also see