Really does depend on the person and the exact weight of the springs
If you are very fit, athletic or have a very good technique you can use a much higher weight
Just as Bio I think he is 30 kg over at the last count and he can bounce 40+ kg higher but not as well
PJ springs are marked on the bottom and if you buy 100's they can be any weight between 100 and 109
Also 90's can be between 90 and 99
So as you can see a set of 90's can be almost 100's
Look on the bottom of the spring and see what number is there
But most of all enjoy them
and don't worry to much
Jason