Your TrueSkill rating is composed of two general elements. One is called mean (or mu) and another is deviation (or sigma). Mu is what level the system is 50% confident you can play at, with sigma being the deviation from said level. Counterintuitively, neither of these are what you are shown in the client as "your rating."
Why is this? Well long story short it's a way to give a leaderboard that doesnt immediately place new players well above their actual level as they often start with a large mu but also have a large sigma in turn which allows them to match with a large variety of the game playerbase but also their initial game results are immensely helpful in placing them at their actual skill level.
Think of it as meeting a person for the first time. The first 5 minutes of conversation with him are often going to shape your impression of them much more than the 500-505th minute of conversation (this is the high sigma), but you have no idea if the guy is going to be chaotic evil or lawful good, so you start at total neutrality (assuming neutrality is the most common type of person, this is mu).
Anyway, back to the Matchmaker. The FAF Matchmaker is divided into a few segments for maps, <300, 300-800, 800-1300, 1300-1800, and 1800+. These rating divisions are based upon your mu, not your actual shown rating which is mu-3*sigma. There is currently no easy way to find your individual mu, however, we are working towards removing the shown rating element for the matchmaker and will instead present an individual player with their mu rating.
If you would like a simple way to gauge your current mu, players typically settle in with around a 100 sigma on FAF due to the specific way our implementation works. So just imagine adding 300 rating to your current shown rating, and you have a general estimation of your mu value. Do note this is only really going to be an accurate estimation after a dozen or two games.