Tournament Earnings ARE added to your "Earnings". Earnings represents credit prizes AND other prizes (Gift certificates, trips, Skycaddies etc). SOme are tangible cash value prizes others are WGT Credits only good on this site.
There is no such thing as "redepositing WGT Credits back to your credit card." (i.e. Cashout).
The point of the Earnings Stats = A way to show the successes of the players on the site. It's for fun.
To see what you earn on each Tourney - Go to "My Account" (near the PLAY NOW button) and go look at "Transaction History."
I think that answers all of it. Regards, AtlantaCoaster