The schedule 1 includes all claimable non-refundable tax credits, including the Basic Personal Amount at field code 300 (line 1). The amount at field code 350 is the sum of all credits multiplied by 15% for the federal tax credit. Included in the field code 350 amount is also the total of the donations tax credit.
So we should sum lines 3 to 19 and not just use line 350, although TurboTax Online's wording seems to suggest line 350. Some has used line 350 instead of summing lines 3 to 19, from what I read in your Q&A!
If you are calculating the amount of Eligible Tuition to transfer from a Child then use only the total sum of lines 3 - 19.
The schedule 1 includes all claimable non-refundable tax credits, including the Basic Personal Amount at field code 300 (line 1). The amount at field code 350 is the sum of all credits multiplied by 15% for the federal tax credit. Included in the field code 350 amount is also the total of the donations tax credit.