Download link: https://modelman.itch.io/fitframe
Created by me: Hossein Alinaghipoor aka Modelman
Well, just give your duration, frame rate and start frame to FitFrame and it'll tell you the last frame. Then you can copy to your software as your end frame. Also, you can kill those ants, change the theme, and reset FitFrame. Download and Enjoy :)
I made a software to fix this problem!