Timing marks.

See, another good reason to check everything upon assembly. Just because the manufacture calls it, doesn't make it right. I use the "0" mark on the cover. Ignore what is on the balancer. Set the crank at true tdc, use timing tape on the balancer.

On another brand of motor I use that in reverse. I set the actual tdc with the balancer/crank and move the pointer on the cover to line up with the zero on the balancer.

You "have" to use a piston stop and a degree wheel or dial indicator to be accurate.