I have a quesiton,

I would like to have an IR Camera (mostly for the hell of it) but I also would like to add a DVR to it so I can (if I want) watch the videos later.

I found some online but they dont tell me how long of a video I can put on there...

All they said is that it can hold 2x 250GB HDDs and that the options for video quality are:

Low 12K Bytes/ Frame
Normal 15K Bytes/ Frame
High 20K Bytes/ Frame

So I dont know if I am doing this right but is this a way to find out:

example 20 mintues of video x 60 seconds = 1200 seconds x 30 Frames/Sec = 36000 frames x 15K Bytes (Normal quality) = 540000K Bytes. So that divided by 1024 will give me MB right? sooooo all in all.. a 20 mintue video will be around 500MB? is this right?