Battery issues? Slight discharge while in stop.

Hi. I've got from a local seller a new battery for my Macbook, last serial letters VMN.

As instructed here, I'm now using Coconut Battery to keep it monitored every time.

I noticed that, if I let my new battery charge, it easily reaches the 5400mAh promised on its box, and the upper menu tells me that the battery reached a full 100%, green light.

But when I put it in stop, still with the magsafe on, and still with its green light, after a couple of hours, for example, I get a 99% charge, and Coconut tells me that I've now a charge of 5346 mAh.

I've never noticed such a comportament with my older, cheap battery that, however, kept charging to straight 100% even when I plugged it at 99%.

This battery, correcly refuses to be charged if too close to the dreaded 100%. No problems if I let it go under 95%.

Is that normal, is my battery slighty defective, a power cord issues, or a Macbook issue?

Of course I've already tried to run the Apple Hardware Test, with good results.

I even tried to test with the power cord of a friend's macbook pro.

I've noticed, though, that Coconut Battery, when my unit comes out from the stop, registers a "Battery power usage" of roughly 3 watts, whatever it means, going to zero if unplugged.

I've also noticed a sort of "pattern": when, in stop, the battery discharges under 97%, it charges back to 100%. Twelve hours of sleep without the lid on, and it discharges to 97% and reaches 100% again.