I assume you are trying to adjust the valves after seal replacement? If so, you need to be sure you are at TDC #1 cyl and on the firing stroke as well. If you're not on the firing stroke then all your valves will be loose.
The camshaft turns at half the speed of the crank, so yes, you will need to turn the crank twice to get the cam to turn once. Follow the firing order starting with #1, turn crank 1/4 turn, adj next # in firing order, etc.
Being on TDC exactly is not critical, just mark the balancer's 0 degree mark (dab of white paint works great) and put it on the timing tab and just eyeball the 1/4 turn, no need for precision here.

BTW; seal change and valve adj take place at the same point, so you can do both at the same time. Also, the cam lobes are at their lowest point during this procedure.