I'm a self-employed sole proprietor, calculating my allowable SEP IRA contribution for 2022. How much ca I really contribute?

I've never had a SEP IRA before. I read once place that I can contribute up to 25% of my modified adjusted gross income for 2022 to a SEP RIA. Another place, I read it's only 20%. I am not sure whether I can contribute 25% as my own employer, and another 20% as my own employee, or what. What percentage actually applies to me? Percentage of what? MAGI?