I just purchased a 64 gig P2, E series card today. I have a training seminar that I'm shooting coming up and it has some pretty long sessions so I'll be recording in DVC Pro on my HVX200a. EVERYTHING that I have seen online says that I can expect to record 256 minutes on this card. I just plopped it in the camera to check it out and record a test and it says 277 minutes. It's the same whether I'm shooting 30p, 60i or 24p...so do I really get 20 extra minutes? Is there something I'm missing?