It's not clear what's going on there. Employer paid health insurance is not reported in box 5 of a 1098-T, even at a university. If anywhere, it's in box 12 or box 14 of the W-2. The most likely explanation is you're confused.
But the simple rule is that anything in box 5 is tax free if used for qualified educational expenses (QEE). Your QEE are shown in box 1 of the 1098-T. The difference between the two is taxable income (if box 5 is more than box 1). You may reduce the taxable amount by any other QEE you have, not shown in box 1. e.g. books.
