Retirement tax questions

Now I think I know what's going on.


When I click on "Maximize Contribution to Individual 401(k)", it is already assuming I will contribute the maximum, but it doesn't really say anywhere the difference vs. what I already contributed. 

 

on form 1040, Part II, Adjustments to income, line 16Self-employed SEP, SIMPLE, and qualified plans, it shows "X" more than what I actually contributed so far. So I'm guessing I should contribute X - actual contribution?

 

Is Turbo tax considering the income to estimate that maximum? (As there are some rules around that)