Also launch day Mini at 100% health. Batteries come with varying capacities when new, not exactly the same. Coconut Battery reports design capacity at 2214 mAh, however my battery is over that at 2245 mAh currently. I happened to save status on Dec 9th and it was 2250 mAh. So if we go by those numbers, I started at about 101.6% health (capacity). Now Apple will never report health on the phone over 100% and doesn't even publish rated (expected) new capacity to avoid exactly these concerns. But let's say the manufacturing variance is plus/minus 1% of expected capacity. That means there will be a number of phones that always report even new at 99% (assuming Apple uses the widely reported 2214 number).
Really isn't anything to worry about. If capacity drops below 80% during warranty (or AppleCare) period, you will get a new battery for free. If out of warranty, it will be $69 if you use Apple for replacement (third party will be less). That is a pretty small percentage of what your phone is worth so don't worry, be happy!
That said, I'm only charging to 80% daily in an attempt to lengthen battery life. More than enough to get me through the day easily.