When to use VFR?

[Akai-Shuichi]

I'm just wondering if there is any certain way to tell if a source is mixed framerates?

For example one I am working with, in DGIndex it says it is FILM 99.94%

and then when I output timecode file it says this
#VFR Stats: FILM cycles 21353 (59.4%) NONFILM cycles 14612 (40.6%) TOTAL cycles 35965
#VFR Stats: FILM frames 85412 (53.9%) NONFILM frames 73060 (46.1%) TOTAL frames 158472


thanks in advance