I just learnt this too, it's about 9 months but counted as 40 weeks. Funny how doctors count from your last period and not conception na. Anyone else found that confusing at first?
My baby was delivered at 39 weeks by C-section and that was full term. Don't worry too much about exact days, your doctor decides the safest timing for you and baby.
My gynac explained it nicely, they count 40 weeks from the last period date. 37 to 38 is early term, 39 to 40 full term, and after 41 they keep a closer watch. Your doctor will track your due date for you.