My gross income is $100,000. At what Alabama income am I required to file a nonresident Alabama return?

https://www.revenue.alabama.gov/faqs/who-must-file-an-alabama-individual-income-tax-return/

The terse Alabama instruction: "Nonresidents must file if their gross income was over the allowable prorated exemption."; is the reason for my question? I need an example of the calculation.