Good SAC rate is something that some have and others do not. Part is the physical makeup of the individual. As pointed out alerady unless the dives were the same profile you were likely to have different rates.
The more you dive and streamline your self and equipment, the more overall comfort you have in the water the better you will find your SAC.
I seldome can make more than 2 hrs on my HP 100’ at 50’ . . . but that is me in the cooper river :-)
YMMV
Best Fishes!! [