For what it's worth, the "IPB days" are basically a place holder, that give 4.0 virtual credit per day. This allows ALPA workers to block off days they plan to work in the office. ALPA people on full time leave are instructed to place enough IPBs to hit the bottom of the window, maybe leaving one week open to fly. Those on part time leave are only supposed to IPB the days they intend to work, to ensure no trips are assigned those days. For all of the above, final pay is based on the office days worked (at the rates in the contract) plus trips flown. ALPA workers also have to obey the 1/7 per week and min day off per month provisions that apply to line pilots.