Depends on the company. SKW for example gives you "virtual credit" of 2.5 hours per day. You don't get paid for this, but it goes towards your min credit in PBS. A typical 4-day DWE (2 days drill plus one day on each end for travel/rest) would reduce your PBS award by 10 ten hours. This prevents PBS from building a full line around the DWE thus cutting into your days off.

If you notify the company of mil duty after the bid, they just clear your schedule if there was anything on those days.

I assume other PBS companies are similar, although I have heard rumors of places where pilots are "encouraged" to bid around mil leave.

But generally airlines are pretty supportive of reservists...I know federal civil servants who get hassled more than I do.