You can quantify the amount of stretch you are getting by looking at the scribe marks on the tension rods. I usually wear mine with just two lines showing. When I notice more lines showing due to stretch or the PM sinking into my fat pad, I adjust the tension rods until there are just two lines showing again.
There is a period of getting accustom to the feeling of the PM stretching. When I first got mine, I could not wear it for very long at all with only 2 lines showing.
Remember, the PM is a very long term growth mechanism. It is not designed to pull your dick out from inside you in a week.

Take your time and wear it with a level of comfort that makes you happy and that is convenient for you. By convenient I mean how quickly/easily you can remove it withtout others seeing you tear off your pants and release the PM. If you're in an office with only 1 bathroom, you probably want to wear it with a little less tension in case you have to wait a few minutes to remove it if it becomse uncomfortable.
Good luck and good gains!