My broker issued a T5008 form. The numbers in boxes 20&21 do not take the ACB correctly into account. Am I allowed to modify the T5008 in TurboTax to correct that?

If I modify the T5008 form, the form my broker submitted to the CRA will be different from the one I submit to TurboTax. I am afraid this might cause issues. Do I have to inform the CRA somehow which modifications I made to the T5008 form and why? If so, where in TurboTax would I enter these notes?