Can my contributions to Self-Employed 401k + to IRA total more than total earned income? Or am I limited to my total earned income between the two?

We have total earned income of $20,000 on Schedule C (no other earned income). 

TurboTax is allowing $5,500 for my Roth IRA, $5,500 for my spouse IRA... AND also indicates I can make  a contribution of $18,000 to my Self-Employed Roth 401k. Is this right, or are we limited to the $20,000 earned income between our IRA's and the 401k? Thanks!