I honestly have no idea, but I'd let hiom know you thought that's what he had agreed too? Not sure whether you have 'a leg to stand on' as such though??? I dont know I really hope so, for your sake...
Um, I think in our maternity leave work site agreement we have to let them know 10wks minimum of our intentions with maternity leave, but I ended up leaving a week earlier, but also 4 wks prior to returning I had to let them know what i wanted.

With next bubba I will ask to have 4 days at work instead of 5!

Good Luck!