When I opened my new bow I found a piece of string looped in the string about where a peep sight would be. Was this string put there to show where the string needed to be separated to insert the peep sight?
It has nothing to do with where your peep should be. It's just there to separate the two bundles of strings in half so you have equal amount of strands on each side of the peep.
Peep location will depend on how and where you anchor, the A2A of the bow, draw length and other factors. It's completely an individual determination.