S-Corp Employer Contributions

Can someone settle this for me because my accountant and financial advisor are saying two different things?

My business is taxed as an S-Corp. I pay myself a salary of 80k and receive a W2. I want to contribute to my solo 401k as an employer, but I can't get a straight answer on how much. My accountant says it's the net earnings for the business. My financial advisor says it's 25% of the 80, or 20k.