Heat -Hens-Roos

[livinghigh2000]

Hello,
I have been hatching Texas A & M quail my statement / question is I have 2 fan incubators set the temp on 99.5 and as my heat rises during incubation I cut it back and keep it on 99.5 cut off out of 34 eggs we hatched 6 roos and 22 hens, if I let the heat go up I have about 50/50 or 60/50 roos but when I keep the cutoff point at 99.5 my hatchdate is more like 20days instead of 17 to 18 days would someone enliten me on this or am i just lucky.