I took the numbers from a ubi forum post on the same subject. I just input the depth in the right corner dial. I use radar depth far more then decks awash so I won't be swapping depths for snorkel
Interesting observation at night using deck awash off Wewak with a Japanese DD way off my beam (plenty of atmosphere-very calm waters, it was real dark, no moon and there was thunder). Looking around with decks awash he didn't see me. I surfaced and my radar -after a few sweeps- told me he was coming my way. Pulled the plug and went deep. This sim has it's moments.
And the number in my screen capture keep my feet dry-you can use the bridge-but nobody is on it.