The Start Over-pull button on the Settings page will begin the first part of a pitch-raise, which is the pre-measuring. The entire process is described here. Pre-measuring is the process whereby the software listens to all the C, E, and G notes on the piano to make a quick measurement of the pitch. Before starting a pitch-raise, it is important to have a tuning file loaded, because once the process starts, you cannot change tuning files or make a new tuning file. For large pitch raises it is often best just to use the pre-packaged AVG tuning instead of trying to make a custom tuning for such a flat piano.
Once you activate the Start Over-pull button, you will hear VoiceOver say "Play C1". You should immediately play C1 and hold it for a bit less than one second. Then VoiceOver will say "E1" and you should immediate play that note. Try to leave a very short period of silence between notes by letting up the key before playing the next note so that each note sounds distinct and separate from the one before it. This process continues for all 22 notes going up to C8. After C8 is played, the software automatically switches to tuning with over-pull by selecting A0. At this point you should tune straight up the scale, tuning unisons as you go.
If you stop playing notes before the end in pre-measuring, the software will recognize this pause in two seconds and go directly to over-pull tuning mode. If accidentally you play the wrong note during pre-measuring, you will have to start over-pull from the beginning from the Settings page.