There's not one simple answer to this. Basically you have to know what the box 4 adjustment is for. You being refunded money is a common reason. Your billing statements from the school may or may not provide details.
From the IRS instructions for form 1098-T:
Box 4. Shows any adjustment made by an eligible educational institution for a
prior year for qualified tuition and related expenses that were reported on a
prior year Form 1098-T. This amount may reduce any allowable education credit that you claimed for the prior year (may result in an increase in tax liability for the
year of the refund). See “recapture” in the index to Pub. 970 to report a
reduction in your education credit or tuition and fees deduction.
