he helped me with this a few months ago. i was looking on the "sidewall" of the "tire". the marks are where the "tire" hits the road. it looks like a tiny ruler when you find itThe indent has nothing to do with timing. Look more closely at your harmonic balancer, there's actual numbers and marks that are etched into it, they can be hard to see.
You'll want to grab some white/yellow chalk or a colored pencil also works, and mark 10* BTC, then use the timing light and rotate the distributor until the mark lines up with the arrow attached to the block.