Is there an earned income contribution difference for Roth 401k and Roth IRA?

Someone confirm something for me, I can’t trust AI on this one.

Anyways, if I work for one to two months and put my entire paycheck into my 401k equaling 7500 dollars, does that mean I can still contribute 7500 dollars to my Roth IRA?

I’m getting confused because I thought earned income was what I take home, and since I put my entire check into the 401k, I took home zero dollars.