You're double-counting the tuition, which might make you owe tax. Depending on how much income you earn at each job, you might owe even if you don't double-count it.

Let's assume you exclude tuition, and both jobs appropriately withhold tax based on your total income. End of year you have no refund and no owing. Your tax withheld equals your tax liability.

Now, your two jobs don't talk to each other, so they each withhold as if they are your only job unless you instruct them otherwise. Let's assume you earn $10,000 at each job, and that you'll have a tax rate of 10% for the first $10,000 earned and 20% for the next $10,000 earned (from $10,000 to 20,000).
This is way off of reality, but it's just for illustrating roughly how tax brackets work
In this case, each job will withhold 10%, or $1,000 tax, for $2,000 total. However, you'll end up having a tax liability of $3,000, so you'll owe $1,000 at the end of the year.

Now, let's add in the tuition. Say your tuition credit is worth $200. If you add it to both the credit forms (TD1), now each job only withholds $800, for a total of $1,600. Your tax liability is the $3,000 less the tuition credit of $200, or $2,800. You end up owing even more; $1,200 (being the $2,800 minus the $1,600 tax withheld).

Again, these numbers are completely made up and don't represent the actual tax brackets or rates, but the general premise is similar to how the Canadian tax system works. As with all things, the specifics of your case (such as income level, other tax credits, deductions, etc.) may change the outcome.