Input on belt tensioner setting

Trying to adjust belt, instruction in stickies says adjust to 2nd mark, I don't see a second mark on tensioner? there are 2 white dots on mine and a line ,1992 M103, my son says he hears a noise when car shifts gears and A/C is on, like something slipping, I'm thinking loose belt, I did replace water pump few months back and had to remove tensioner, I tested it and it passed the 30 degree test so did not replace it, belt seems tight but double checking adjustment, has a new 6 month old belt also, check out this pic, anyone see a second mark?
Thanks for any input on this!