The voltages are the charge controller settings for different uses. The 13.8 figure is for float charge when the thing is mainly not used but available for stand by .

The higher figure is to fully charge it if you regularly discharge it a significant amount.  Quite often many uses use both figures. An initial charge to the higher figure to get it fully charged and then you drop to the float figure after it has been at the higher figure for an hour or so. Usually you  work at the lower end of the high figure for normal use and occasionally give it an equalising charge at the top end to make sure all the cells are in peak condition.

The initial charge current is the current figure they recommend that you don't exceed  in the early stages of charge, the controller will taper the charge off in the later stages and the current will be low at the end of charge.

The initial charge current seems rather low and possibly this type of cell is not really designed for very large discharge currents either.

Float would be something like a burglar alarm where it is not normally used but is available if the mains fails.

Most RE use falls between these extremes, you will be using load regularly but you have some charge at the same time. Solar tends more towards float if you have plenty of sun regularly ans large panels. Here in the UK it can become cyclic when we have days of no sun. Wind is normally more cyclic than solar in most areas.