New Battery Voltage and SG

One thing you may find on SOME battery company websites is that it takes a few cycles to "Break them in" .. Now just what that means in terms of what you observed I can not tell you..

Best advice: continue to charge, and keep an eye on 'em.

I too find my GC-2's can hold a good surface charge for 4 or more days, easily, and then SG's are in the 1.275-90 range. (at ~70F)

You didn't get there yet, but right idea to charge them up right after buying them.

They need an "overcharge" to reach "baseline SG" after being on the shelf at the store. My GC2-XHDs were 1.300 SG baseline when new at about 40F ambient. Four years later, they are still close to that.

After the overcharge to 15+ volts, then next morning they will be at about 13.2v then be in the high 12s next day. Takes quite a while to lose the surface charge. Slow self discharge after that.

http://pdf.wholesalesolar.com/battery-folder/charging_instruction_2011_2.pdf