In that case they were simply adjusting their station keeping schedule and minimum (if any) fuel would be wasted. If that wasn't the case, they could raise or

In that case they were simply adjusting their station keeping schedule and minimum (if any) fuel would be wasted. If that wasn't the case, they could raise or lower the altitude slightly several orbits before the "event" causing them to arrive at the intersection point earlier or later. For a desired time delta, the sooner your perform your altitude change the smaller the changed required.