Advance the timing before TDC. Why?

Hello guys. My question is to learn the purpose of what I did.
This is the engine; 318ci, bored .020 over, stock pistons, 302 heads decked to 58cc (ported), Edelbrock Performer intake (ported), Edelbrock 1406 600cfm Carb, Comp cam XE262H Duration 262/270, Lift .462/.470, stock distributor

It was recommended I advance the timing on the engine when I tune it. Stock tune is 0 degrees, or TDC. I've tuned it to about 9 degrees before TDC.

Why do I want it tuned that way?
Still related to ignition. What would you suggest for a distributor to replace stock?
You need to get the fire lit at the right time... not too early, not too late. Sparking at TDC can get the fire started to late (or explosion should we say :D) maybe this may help....