The file size can be whatever you want it to be. If you compress it to play back for the slowest DSL (384kb),
you'll get one size. If you compress it to play back for 512kb or 1.5mb, you'll get 2 other sizes. It's simple math,
the data rate you choose (a kb is .125 of a KB, which 1,000 of those KBs add up to a MB, close at least), so data rate times length
of video= file size
kbs=kilobit per second
KBS=kilobyte per second
MB=megabyte per second
Instead of remembering 5th grade math, though, you can use the handy AJA Data Rate Converter (OSX):
http://www.aja.com/html/support_kona3_swd.html
Scroll down to: AJA Data Rate Calculator Application (Version 2)
This OS X software application calculates data rates and storage requirements for a given video size, format, and frame rate. It's great for both KONA and Io users as a resource for configuring systems and determining storage requirements.
Ed