Confused by 2 timing marks

[Country Dirt Kid]

I have a 1981 20 hp mercury serial 5608471. I borrowed a timing light and now I want to verify the timing. I am confused by 2 timing marks on the flywheel. The marks look like a little vertical line stamped into the flywheel and outlined in white paint. Why are there two? Which one should I use to set (throttle pickup timing adjustment?) Whatever that means. Thanks for the help.