OK, so there are 190 teaching days a year. If I work 0.8 of a full-time role, then by my calculations, that's 152 days (have deliberately left out the additional Inset days I do, as it complicates the issue, as they're always on Mondays, which I don't officially work).
I've just counted up how many days (Tues-Fri) I will have taught this academic year, and it comes to 157.
Can anyone tell me how that is possible, before I make an arse of myself by possibly pointing it out to my HT?