No, if the reduced amount does not affect 2016, you do not need to amend 2016. The amount you paid in 2017 can only be used if it was for classes that started in 2017. (last year's 1098-T could have reported tuition BILLED for Spring classes that started in January, February or March of 2017.) This year's 1098-T from your school should have had an amount in Box 1 "Amounts received by the school" but not all schools are doing what the IRS wants them to do. If you have the proof that the funds were PAID in 2017, and that you attended those classes in 2017, you can report that amount by clicking "What if this is not what I paid" under Box 2 on the 1098-T screen.
If your school DID report Box 1, as they should have, the amount you paid should be listed in that box and there would be no need to use the link.
Be sure to keep a copy of your student account records with your tax file in case the IRS questions it. They might, if the school did not report Box 1 and sent them a blank 1098-T.
