As others have pointed out, the "numbers" you are seeing are indeed NTRP ratings. I suggest that you not read the guidelines if you're trying to rate yourself. This is my opinion on how I define NTRP:
3.0: You are not consistent at anything with pace on it, whether you're receiving pace or applying pace is irrelevant. This is mid to high range of beginning levels of tennis. If you're absolutely new, go down a notch to 2.5. If you're athletic but unfamiliar with the game start at 3.0 and no higher.
3.5: You're starting to be able to add pace on balls with nothing on them but you have problems with most of your game pace and spin can still defeat you. You will probably have most of the strokes of tennis down, they may just be a little weak. (Low to mid range high school player)
4.0: You have every stroke in tennis with decent pace and spin. Pace and spin will not defeat you in neutral rallies and you should be able to rally for extended periods of time. If you are not this type of player, you're probably the other type of 4.0, which is the player who has a few advanced elements to their game which they can use to make up for the parts they're lacking. Every 4.0's game is more or less complete and should not have any totally missing or weak elements. (mid to upper range high school player)
4.5: You have every shot in tennis and you can perform them well. You are able to go on offense at will and can play defense. Very few careless errors are made. Most points are won outright or are "forced errors" due to having to play balls out of reach or on the run. (Highest level high school player, or Jr. College player, or D1/D2 doubles players)
5.0: At 5.0 you're really needing to start doing statistical analysis at this point. You have no weak elements, you're "improving" high level strokes. Fitness level is very, very high. A legit 5.0 player probably played singles for D1 and was relatively successful. This level of player has probably experimented with open tournaments and has done well. (This would be a high level college player. Most college players are between 4.5 and 5.0)
You pretty much dont need a rating at this point. You played tournaments and the results of those tournaments are your "NTRP". These types of tournaments typically have large turnouts.
To put this into perspective, the difference between a 5.5 and a 5.0 is that a 5.0 has no realistic chance of even winning a wildcard qualifier. A 5.5 might be able to get away with qualifying for the wildcard, but he has no chance of actually winning the wildcard event.