Magnum inverter, Yamaha Generator

I do not understand. Unless thermal issues interfere, the AGM should charge to 99% or 1% of ampere hour capacity at 14.4 volts potential. When amperage decreases to 10% of amp hour capacity of the bank, the battery should be more or less 95% charged even for the lowest Chinese grade of AGM. With a Concorde battery the percentage rises to 99%.

Maybe someone can explain what the exercise is attempting to accomplish :)

Thank you