A standard lead acid type battery should read about 12.73 volts when 100% charged,
AGM (absorbed glass mat) type battery should read 13.00 volts when 100% charged..
If you check the battery after it has stood overnight after being charged you should get a more realistic reading.
I checked the AGM battery for my 500 that was charged up about three weeks ago its reading 13.1 volts today.
By comparison my 400 lead acid battery still on the bike last charged about a month ago is reading 12.3 volts - I've just put it on charge.
Make some allowance for the accuracy of your volt meter.