Maximum points 255 is the maximum amount of points your teams can score. After that point, the scoring stops recording on the scoring summary. For example, if the play that yields the 255th point is a 45 yard TD pass, for every touchdown after that (be it rushing, passing, defensive or return) the message at the top of the screen will always be "45 yard pass" before it says "extra point". Also, your scoring summary will stop recording. Your passing rushing and receiving statistics will still be recorded (to a point), and the drive summary will still say what you did on that drive.
Maximum rushing and receiving yards 1023 is the maximum rushing and receiving yards in a game. After that point, it stops recording. If you are a WR or RB in Superstar mode, it counts against you for any extra caries (or catch) you have, thus decreasing your yards per carry (or yards per catch). Oddly enoughy, your QB has a far higher passing limit. 8191 is the maximum rushing/receiving yards you can have in a season.