The official way is to count how many clicks there are between bottom and your 100m marker before taking the gun apart, then reassemble to get it back to that point. Most rifles have about 9 clicks or so. But if you needed to crank it to 600, the prior setting wasn't right anyway.
If you have never sighted your rifle in properly to determine how many clicks you need, then the way to do it is reassemble it any old way, then shoot and adjust to sight in at some fixed distance, then loosen the screw on the left side and move the markings wheel around until the distance on the wheel matches the distance you are shooting at, then retighten the screw.
The right hand knob should be tight enough that you get clean, positive clicks on both the windage and elevation knobs, and not so tight that you have trouble turning them. There is only a fairly small range where the elevation knob clicks nicely but the windage knob still turns freely. There isn't a spring but the shaft is D-shaped and needs to line up with the matching keyway to slide together properly.