This is the logfile when I was doing a backup copy of Thor (the first movie).
I used AVI (XVID codec) with MP3 (256/48k) for both test encodings. Left the fps setting alone in both cases.
When I ran this thru DVDFab 12, the FPS property recorded correctly (23.976 fps, or 23.98 as it shows up in Windows properties). Running it through the most up-to-date version of DVDFab 13, shows the 600 fps. I went through the log to see what was going on, and I did not see what caused it to record 600 fps in DVDFab 13 that it did not in DVDFab 12.