Earlier quoted context omitted.
Instead of adjusting fuel you can probably compensate by changing when you do the burn. And there are likely to be midcourse corrections anyways.
That makes me wonder: how is it possible to even determine what the correction should be? Space is vast, how do they determine the position of a microscopic vessel precisely enough to know how much to burn?
Multiple correction burns along the way. For equivalent burns, the later along the trajectory the burn, the smaller its net effect on final position. So it's a series of increasingly better approximations.
Try it in ksp. It's quite illuminating to plan your burns and see their effect graphically and build an intuition for celestial mechanics and astrogation.