Don't worry Gifted, six months ago I was where you are now, but with help from members of this forum the clouds are beginning to lift now.
Back to your R/O
Did you get any paperwork with it? That might tell you the gpd it is rated at - if not ask your supplier.
My 200 gpd is at the low end of the scale and if yours takes 17 hours to fill a 210 litre butt then I'd say your water pressure might be low - has your r/o got a pressure gauge on it?