If you put a multimeter on the battery you will get a better idea of what the lights are indicating.
They probably indicate if the regulator
is in bulk, absorption, or float mode, but this is only very loosely related to SOC.
The load terminals are not generally useful on a boat
, although occasional they can be used to do something like turn off an anchor
light during the day.
The led marked load probably, when its illuminated, indicates the load terminal is connected and therefore would supply power.
Some regulators connect the load terminals when the battery voltage is adequate (so it works as a low voltage cut off), others at night only (to turn lights off during the day). If the load light has remained illuminated all of the time it is probably the former type.
Be aware the load terminals will only carry a limited current
so you may need a relay if you wish to power a large load like a fridge fridge via these terminals (and have it automatically disconect if the battery voltage drops)