The grid charge current (Amps) relates to the DC current (Amps) going to the battery and not the current (Amps) being pulled from the grid itself, so this setting can be higher than your cutout fuse.
For example if you a total battery capacity of 16kW and your grid power setring is 100A
Battery power 51v (from memory) x 100Amps DC =5100w
Grid current 5100w / 230v = 22Amps AC