The pilots are from 0-25% of throttle. The needle jet is from 25-75% of throttle and Mains are 75 to 100% of throttle.
Changing jetting is not as simple as just going lower. If you go to low you burn down the motor, so you need to find out what you need. Typically a run at the determined throttle for an extended period and a hit shot of the kill switch will tell you what you need to know. Then you pull your plugs and take a look at them. You are aiming for golden brown. White is too lean, so you would need larger jets. Black is too rich and smaller jets would be needed. Then you can take a look at the piston wash. Silver areas on the piston indicates the the mixture. A thumbnail size area cleared off by the mixture is what we are aiming for. Lean is tough to tell between rich, but it would appear that the entire piston is clean. However rich can do this as well, but typically a rich condition will just slightly enlarge the silver areas near the ports.