It looks like they modified the vote count by pressing a button every now and then that transferred a fixed number of votes from Trump to Biden. The net change each time looks like it's -6500 + the real net change in PA and -4900 + the real net change in GA.
So it looks like they didn't have the ability to control the size of each "glitch". They could make the glitches happen, and they flipped the same number of votes each time, by a number chosen in advance to be suitable for the individual state.
The ratio 6500 / 4900 is close to the ratio of the populations of PA and GA.
So they chose a number of votes to flip with each glitch which was proportional to the state's population, and triggered the glitches one by one, presumably trying to avoid decreases in the vote totals for Trump, which would reveal the fraud.
Notice that it only happens at times when there have been thousands of real votes. They were trying to hide the flipping by triggering glitches only when they thought the real number of votes would be large enough to hide it.