Spectra s2 stimulation mode?

I've only used stimulation mode on level 4 for so long that I can't remember what level it's supposed to go to.. I thought it was 12 just like expression mode but when I was playing around with it earlier tonight it would only go up to 5... is it always like that or is my pump messed up? I can't remember if it's supposed to go to 12 or not?