Looking for some help on re-charging my Scamp 13 battery - i.e. it's winter and I just want to hook it up to a charger to maintain it.

I have the Deep cycle 27 battery that I got from Scamp with the trailer a year ago. I think the brand is Northern. I bought a batteryminder charger model 128CEC1. But I can't find in the instructions for either the battery or the charger what settings to use. There are only 2:

1) I can set the amp setting to 8A, 4A, or 2A. Which do I use? From what I can read - maybe the 8A seems like what they want me to set at? I assume each one is just the rapidity of the charge - that is 8A will charge it the fastest?

2) Now there are three battery settings: Odyssey/PLT, Wet/AGM/Sealed, or Gel. Which setting should I put it on? I think its the Wet/AGM/Sealed?

Thanks!