How do I know how much of my scholarship is taxable?

I'm going through TurboTax and I'm on the 'Taxable Scholarship and Expenses' section of the income.

 

I am married, filing jointly and my wife is a full time student. She received form 1098-T (no W2 for her), I'm puzzled on how I'm supposed to know how much of her scholarship is taxable. How do I find this value out?

 

There are two boxes in form 1098-T that have numerical values, box 1 (Payments received for qualified tuition and related expenses) and box 5 (scholarships or grants). Is the taxable scholarship amount equal to box 1 - box 5?