A Half An Hour = 30 minutes

In the morning, a discussion about consequences:

Mr. C: Come on S you got time.
S: Man how much time I got?
Mr. C: Half an hour.
S: Y’all be fucked up, I’m only supposed to have 30 minutes.
Mr. C: A half an hour is 30 minutes.
S: Nah, a half an hour is an hour and 30 minutes.
Mr. C: No, an hour and a half is an hour and 30 minutes.
S: Oh… I was about to say, y’all be fucked up.
Mr. C: Let’s just go do our time.