Ferrari Mailing List: Spark plug reading?

[Peter Pless (ferrarilist]

Does anyone know what this means?

http://www.pless.com.au/308plug.jpg

It's from my newly rebuilt 308GT4 engine. 10:1 compression running on
unleaded fuel.

Programmable ignition gives it lots of advance.

When the plug was pulled, I'd come back from quite a long drive, but the
last bit of it consisted of traffic and plenty  of idle speed stuff.

What's with the carbon on it already? Engine's only done 600 miles....and
I've been nursing it.

TIA

Peter