If you left the battery on the shelf for 8 months or more chances are that some sulfatation happened to the battery´s plates because it was fully discharged. In other words, maybe it has no longer the full capacity as when it was new. When it is fully charged the voltage reaches about 14 to 14,5V with a very small current needed to keep this point (called the floating point). After reaching the floating point, if you turn off the charger, the voltage rapidlly decays to 13,6 to 13,2V (in a few minutes) and then goes slowly to about 12,6V with no load. Voltages may differ somewhat depending on the battery type and manufacturer. If you are reading 12,2V it is probably not fully charged OR you are experiencing the effects of a damaged or long time used battery. My suggestion is:
1- Keep it charging for more time and see if it reaches the floating point (just measure the voltage with the charger connected)
2- If the voltage keeps within the expected floating value, leave it charging for more time (1 or 2 days). Usually those batteries recover part of the damage by sulfatation (not all).
3- Apart from the fully charged and fully discharged voltages, any other voltages you read can´t tell you anything about the amount of charge of the battery.