[lnfletcher]

I'd leave the white mark where it is. It's there to make it easy to spot the 0 deg. With the engine idling and the vacuum disconnected from the dist. (if it has one) then set the timing at 10btc under the TIME mark. Rev the engine and make sure the mechanical advance changes but not past the max total timing.
10 deg is pretty advanced. If your trying to get more performance by advancing your timing, your gonna run into pre-ignition if you go any more. IMO