Yeah, well I'm not sure there is any meaning to that calculation. This unit barely will put current into the battery.
Who said it was a constant current charger? It's a tiny wall wart that barely charges the battery. Even a 2 amp charger will fully charge a battery overnight. This thing takes days because there is very little excess capacity compared to the minimum current required to keep the thing up. But then again, I guess it is constant current considering that the battery always draws the full load it is capable of delivering. It's a 15 volt power pack and once attached to the battery it never gets above 13.5 volts. So it does put out a constant current under those conditions.
I don't think charging a lead acid battery is a zero sum game.