Following up on Kihra’s comment, when viewing data that focuses on % rankings (overall or iLvl) there are generally two things you can change that influence what you’re looking at if the default numbers aren’t working for you:
Today vs Historical - If you’re looking at older data and want to see how you did compared to numbers at that point (especially useful if your class has experienced a change - buff/nerf), use Historical.
Rankings vs Parses - Rankings compares to the best ever parse of other eligible players, Parses compares to the last two weeks of parses for other eligible players. I feel that Rankings is the more “fair” comparison.
The different pages still don’t perfectly match so there are other things going on there but I haven’t been able to figure out those discrepancies yet and they’re usually minor.