If you got an initial reading of 13.2 V why would you have taken it off the charger in the first place? It's a brand new battery so it's usually standard procedure to get it 100% charged before installationA normal car only has a parasitic draw of about 50 milliamps. That's not enough to pull the voltage down on a healthy, fully charged battery to 12.4 volts. Even a worn battery will show higher than 12.6 volts right after being fully charged. They call this the surface charge. After sitting for a while, the voltage goes back down to it's normal full charged state.
I got a new Interstate battery a couple weeks ago and charged it up before installing it. The initial voltage after taking it off the charger was 13.2 volts. After I installed it and started the car and turned it off, (thus removing the surface charge) it read 12.7v.
That is hardly what I would call minimal. The difference in those figures is a 1/2 charged battery to a fully charged battery.12.2-12.3 vs. 12.6-12.7? That's pretty minimal and could even be from the resistance in the voltmeter cables.