Oh, sorry, I use a DD-8 and have the same issue, I just turn it 'til it feels good for me. Sometimes I think I should have got the DD-3, it allows for finer adjustment.
The DD-7 even allows for finer adjustment than the DD-8, I would set it to the 800ms mode and use the table on page 14 of the manual and dial it as close as possible. In that mode the dial at 0 is 200ms and at 10 is 800ms, so noon would be ~500ms, adjust from there to the setting mentioned in the links.