RERA after cpap

hi. I just had a split study and am very concerned. My first showed an AHI of 43 w/ 100+ arousals over 2.5 hours. So, cpap of 9 pressure was figured after titration. However, AFTER they left me at this "ideal" pressure, i STILL had an AHI of over 7??? shouldnt it be removed fully or bring me back for another full night titration study? Even more concernins is that i still had 100 arousals during 3 hours and 40 minutes. M rera index went up from 15 or so pre-cpap to almost 25.. so, even though CPAP should "Cure" me, i have an AHI of 7 and REra of 25.. that gives me total arousal/resp disturbances of 30 per hour.. oy... am i wrong or is my doc off base?