Grad student who gets tuition credits - does that count as income when calculating child support owed? [Oregon]

My ex is a full time grad student in another state (but my case is in Oregon jurisdiction). I have filed paperwork to modify the child support he pays to me (I pay him alimony). In his response, I found out he's a full time grad student, with a small stipend, and gets tuition credits.

For the purposes of the child support calculator, can I legitimately argue that the tuition credit should count as income? Or does he get a pass since that income is not taxable?

(I don't have a lawyer, and the review hearing has not yet been scheduled. I'm trying to marshall all my arguments ahead of time.)