If I am reading the O/P right he HAD (past tense) a WFCO so any reference to it is off target.. He now has a Boondockr's 75, which I am not familiar with.
He ran the battries down to 50% so he needed to replace about 116 amp hours He charged at 73 amps..
Was this converter output or battery input?
And only added 10% about 23 amp hours worth...
First... Recharging is not 100% efficient.. I would expect more than that though.. But if you are reading converter out you have loads.. Several loads.. So that 73 amps might be as low as 50 going into the battery. or less.