Export FPS question

Hi,

I've just started to use the Windows Virb edit with my Virb XE. I recorded some footage at 1080p @ 30fps. I put it together in Virb edit only to find when I wanted to export, the FPS options were 100, 50 & 25.

Why isn't 30, 48 or 60 available given they are the recording options of the Virb?

Thanks