It is best to check your Notice of Assessment from 2016 to make sure that the carry forwards of your tuition and education credits are correct.  It is quite possible that your carry forward amounts are that large if you have gone to school for a number of years and your income was too low to use the credits.  If you have a CRA My Account you could also check there to make sure the amounts you are using in your 2017 tax return are correct.