Normal for those of us with ASV units is a "non-starter". By definition, we deal with abnormal breathing issues. What's more important for you is what's normal for you. My wife complains that I tend to breathe really fast. But it's the way I've always breathed. So, periodically keep an eye on it. If you feel poorly the next morning is there any change in your respiratory rate?
As to what's normal? Variance is pretty normal. Below 10 is not all that normal, but might simply indicate a deep level of sleep. Above 20 is also not all that normal, but might just indicate wakefulness or REM sleep.
http://en.wikipedia.org/wiki/Respirator ... rmal_range
Remember, since we have problems with breathing anyway, "normal" for you and me is typically off the "normal" chart. The bigger issue is if it is abnormal for you. If it is, then consider discussing it with your doctor if you also feel poorly. If you feel fine, then keep an eye on it.