I wouldn't worry too much about all the figures on that web page. Most of the important information is in the title. 12000lbs maximum line pull would be more than enough to winch a discovery about and the first figure in the table is 12 volts so basically it should fit and work, However.... there has already been a lot said about cheap winches from non established brands on this forum and many others. Personally I would describe the quality of this sort of winch as variable. Some people get on ok with them and then there are others that don't.
As well as ebay, keep checking the for sale sections of forums, I bought my Superwinch EP9 from a member on this forum second hand, but in new unused condition complete with an additional unused synthetic rope and hawse. It wasn't the bargain of the century, costing a fair bit more than that one on ebay, but was still very reasonably priced and has since proven to be a very dependable winch.