Simple Query: Pocket pairs/X hands

[Jeff W]

Please correct me if I am mistaken:

I am dealt a given pocket pair 1/221 hands. So, to find the the number of pocket pairs I should receive over X hands, I use the following formula.

(X*13)/221

Seems pretty simple to me, but I noticed I'm off of my pace for pocket pairs by 32 hands(151 Pocket pairs in 3114 hands, where I would expect 183), so I wanted to make sure.

Thanks.