A string, be it bow string, piano or guitar, has nodes along the length of the string that emit sound the most. These are at intervals of 1/2 the string length (being the loudest), 1/3, 1/4, etc. decreasing in sound level as you move out. The best dampening will be at those nodes as measured from the point where the string touches the limb. I prefer the 1/4 distance as 1/3 gets the yarn puffs I prefer a bit too far down the string for my liking.
I won't pretend I can explain it, because I can't...but I know from experience that it can vary.
A fellow I know brought a bow to my shop that he was having fits with--couldn't get it quiet. Tried the 1/3 points, the 1/4 points, and both at the same time (two sets of silencers). I thought he must be doing something wrong.
Removed the old silencers, tied on some rubber silencers so they could be adjusted, and went out back to shoot.
Shoot, adjust, shoot, adjust, scratch head, measure, shoot, adjust. What the?????? I had gotten frustrated and gone inside to cool off. He stayed out back shooting. In a few minutes he hollered--he'd found the spot. That bow went from very loud to a whisper. He'd moved the silencers out to maybe 5-6" from each end--where, by all accounts, they shouldn't have been very effective. For whatever reason--maybe the way the bow was tillered?--that's where they worked.
I've also seen bows where moving the silencers about an inch made the difference in noisy and hunting quiet. Dunno why, but I do know that there's no "one size fits all" answer. Like most everything else in this sport, you have to tinker and experiment to get the best results for your personal equipment.