Not familiar with the gun but it looks a lot like a spyder type of paintball gun.
The lower tube on the body below the bolt (part that sticks out towards your face when shooting) there is a little screw sticking out and typically you would just undo that and then turn the bigger part to where you want it to be. Then proceed and tightening the smaller screw.
I read a little and it shows it will only go down to 250 (probably because the type of spring you are making tighter/looser when you tighten up what i mention above. So if you still have that problem of shooting to high or low you will need a new spring more than likely.
Like i said, not totally sure since i'm not familiar, just looks very similar to spyders I use to own.