FX Tuning Question for Impact

I have a .25 cal Impact MKII on which I swapped the old power wheel for the M3 power wheel.

I noticed that power setting 8 has a circle around it. Guessing that indicates something besides the obvious "half way point." What that might be, I don't know
When tuning, is it advised to tune from the "8" or should I set the wheel to the highest number 16 to start using the fine tune screw for max velocity at a particular reg setting?

Thanks,

KP
 
I always assumed the circle around the 8 was just a reference to halfway. I personally always have my wheel set on its highest number when I find the peak speed for my reg setting. That’s because I always reduce hammer strike as I tune the gun. Then if I decide to increase my reg setting it’s right back to 16 on the wheel and I start the short search for my new peak speed. So basically until we somehow start finding good settings by smashing the valve harder than the reg setting will allow, I will just keep the highest number on my wheel as the fastest the gun will go on a particular reg setting.