Why does a netbook battery wear out?

Question

laptops

I bought a Lenovo E10-30 netbook in winter, a 2200 mAh battery. I rarely use it, just over a dozen charge-discharge cycles have passed, but the battery capacity has already fallen by 14% (according to Aida64).
What can be wrong? I usually discharge up to 5%, charge up to 100%, with a charge below 10%, it does not idle for me, I use it at home without a battery, from the mains.