If you contribute 6% of your salary, you will receive an additional 3% (of your salary) "match", which is 50% of what you contributed. If you contribute 4% of your salary, you'll get an additional 2% of your salary as a match. If you contribute 2%, you'll get 1%. If you contribute over 6% of your salary, you'll still only receive 3%, since that is where the max comes in.

Disclaimer: I do not run your 401k.