Copying the subtool and re-pasting the undo history with a saves the undo history from finished project to make a have no undo history at. rcording
For example, if you have steps A, B and C you can undo back to step A. Increasing the HFrames setting will have an impact on the movie recording time and the final movie playback speed because of the extra frames added to create a smoother movie. Having this message means your Undo History will be lost beyond the current point. The purpose of this option is to prevent you from accidentally deleting your history while navigating through it.
