The Family Finder’s relationship ranges cover most possible relationships between two people. It takes into account several factors. These include the total number of shared DNA segments (blocks) and the total number of centiMorgans (cM). For the immediate and close relationship ranges, this is highly accurate. The nature of autosomal DNA means that the expected values will vary more in the distant cousins range. This means that the ranges are wider, but they are still accurate within a given range. The speculative category is exactly that, speculative.