spark advance

[dziiq]

Welcome,
i have a question - error P0330 appeared in my fiat bravo 2.0 20v 99'. I've checked spark advance and its between -35 deg. and 10 deg.
In my friends seicento spark advance is between 40 and -10. What does it mean when the spark advance has minus value? If i have -35 deg. advance, does it mean that spark is after TDC or before? Seicento works fine, but Bravo hardly accelerate. I know knock sensor may retard ignition, and as its broken it might force ecu to retard ignition so much?

Regards, dziiq

stopni = degrees