It's supposed to be 5lbs a line so 5-10-15 but it always pegs out on mine and I cook on the lowest setting on a gas stove.
I usually leave the jiggler off till I see steam coming out then put it on and lower the heat when I see it rise to the 2nd mark and turn it down to low. Maybe I'm doing it wrong but it works for me.
Here's a download for the manual, the download button is on the top right.
http://libcdm1.uncg.edu/cdm/ref/coll.../HENP/id/12226