some doubts about my new notebook battery

I bought a brand new hp mini 110 battery replacement (HP Mini 110 Battery 6 cell 5200mAh 11.1V) the detecting software BatteryMon shows that the capacity has lost 8.6%. The original capacity is 5200mah, now is just 4800mah available.It is hard to understand. Whether it is a normal phenomenon? Seeking explanation, thanks advanced!!!😁

Additional question:
I discharged the battery completly, then recharged it for 12 hr and rebooted it up, the capacity the computer showed is 4685mah, didn't reach to 4700mah any more. Did problems occured? I need answer urgently!