So just a bit on non spoiler clarification on the rankings that's not really explained in the show. All the lower ranks (E-A) are set numbers, say 1-10,000 for example, where each 2k is a rank. They can define each hunter's rank within each of those, so 2 A ranks, where 1 is 8,500 and another is 9,200, while both being A rank they know which one is technically stronger.
S rank is a bit different, where the machine can only read up to that 10k mark, so anything over that is considered S, you could have someone at 10,001, or 40,000, and both are still just S rank, but they have no way of knowing who is actually stronger unless they fight