I would pay the additional amount so that you don't incur any interest or penalties.
I don't know why the CRA made changes to your return - again you would have to look at your full NOA when you get it to see what was changed and why. If it does turn out to be a TurboTax error, you can contact our phone support team and ask to submit a claim under the TurboTax 100% Accurate Calculations Guarantee.
