State tax filing
The formula for income taxed by both jurisdictions is your Oklahoma wages less your Oklahoma itemized deductions less your Oklahoma exemptions. This is on Line 11 and Line 12 of your Form 511NR, respectively.
The tax comes from the Oklahoma Income Tax, Line 19 of the Form 511NR.
I did a mock-up return for a single taxpayer making $50,000 in Oklahoma as a Michigan resident. As you can see below, the income taxed by both jurisdictions is $32,000. This is because the itemized deductions are $17,000 and the exemptions are $1,000. The $1,413 flows from the Oklahoma Form 511NR, Line 19.
