Retirement tax questions

I'm self-employed. In the section on "Your retirement Contributions" it says "Here are your self-employed retirement deductions using the maximum allowable contribution. Note: The maximum you can defer to all your 401(k) plans is $xxxx, and you can put more into your plan as profit sharing. Maximum Allowed to Qualified plans: $xxxx" I understand the words Maximum Allowed, but it's the part talking about deferring that I don't understand. Thanks.