Leave is credited at 2.5 hours/day.
However that credit value was originally calculated on an expected 80+ hour month, not 90-95 hours as is the norm on the Airbus MFF.
So if the build requires, say 93 hours per crew member as an average, then somebody with 6 days leave can expect to do around 78 hours flying, that also being the productivity threshold for a 31 day month.
This means that the company gets the leave for free. Great for the accountants. Not so great for the crews with fatigue/lifestyle issues.
But the manual roster insertions do not take into account the 2.5 hours/day, they are added at the whim of the scheduler who will be trying to cover flights with insufficient crew numbers.