Ok, so...when you set a heading at 000 degrees and then you rotate to 30 degrees and hit “Start” button it seems to subtract 10 degrees and only reflect 20 degrees (but it should show 30). When you select “Reset Heading” it resets it to 20 degrees and that is your new heading. This is with “Magnetic North” selected in the main compass widget.
Now, on a hunch I went in and changed the compass widget to look at “True North” as opposed to “Magnetic North” and went back into the Dive Compass and when you go through the same process as I described before, it works properly. So, when you have MG selected the UW compass “Reset Heading” works incorrectly and when TN is selected, the “Reset Heading” works fine.