Is it measuring events while you're using the CPAP? Or while you're sleeping without any breathing assistance?
I found this scale from Harvard that says "mild" apnea is defined as 5 - 15 events per hour.
Anything under 5 per hour is normal. The question is would you only have 1 per hour without the machine?
Your cpap is correcting your apnea to where you are in a "normal" level. The best way to determine whether or not you still need it is to do another "diagnostic" sleep study. This can be done at home or in a lab.
A cheaper alternative would be to do an overnight oximetry on room air. It won't see apneas but it will see the spikes in your heart rate in relation to any desaturations that you may have.