So, for every week of vacation you lose 3 off days, on top of that, the vacation compensation is based on your basic salary which is roughly a "fourth to a third" of your actual salary with the flight compensation.
Expecting some shafting of the pilots for 2-4 months during the winter season with no prior proper notice. Unless Rome is particularly popular during the winter months. If you've signed up for these terms you probably wouldn't mind some further shafting.
Separating flight pay and basic salary under very ambiguous terms triggers warning alarms here.