Storege capacity with DV NTSC!!!!

Hello everyone. I have a problem with the capure settings. I have arround 400 free GB on the hard drive, with the DV NTSC 48khz capture preset I only have arround 200min. of storage. I switch to DV NTSC 48khz anamorphic and those 200 go to 900min. Where is the trick? What I am doing bad?

I have I Blackmagic card on a 2x3Ghz Dual-Core Intel Xenon. 4gb ram. FCP 6.0.1

Which is the best configuration for capturing DV NTSC with the blackmagic?

Thank you very much.
Hector Bragado.

DV NTSC does not require a capture card, rather all cameras I know of use a Firewire capture.

3.7 MB/sec is the data rate and 1 hour of DV takes about 11 GB of disk space.

Thanks John.