For whatever reason the timing marks on my PV's engine don't really seem to be anywhere reasonably close to being correct. But in any case I usually don't pay too much attention to them. I just advance the timing until I hear a tiny bit of pinging under a load, then back off slightly. That will generally give you the best (most advanced) timing given all the variables (engine's current compression, gasoline octane and quality, plug type and condition, etc, etc).