You are basically borrowing a specific vacation days pay and putting it on a dropped trip, for every IVD day, so say last summer you did an IVD to drop a 3 day and used 3 days of IVD, from your FEB vacation. When you did your bid for FEB, instead of having the 3rd of Feb to the 9th of Feb off, it’ll have the 3rd thru 6th Feb on your line for vacation, assuming you told Icrew to use days 7, 8, and 9 from your vacation.

The nice thing is, since you lost 3 days of vacation pay, PBS doesn’t prevent you from getting a trip on the days whose pay you borrowed. Does that make sense?