Technically both are correct.
The first question on the page where you enter your dependent's MAGI says "Are any of your dependents required to file a 2016 tax return?" One way to determine this is if they have taxable income (on line 6 of the 1040EZ). TaxGuyBill was basically giving you an easy way to determine if your dependent is required to file a return. If you answer "No" you do not have to enter your dependent's MAGI which is what TaxGuyBill instructed.
However, if you answer "Yes" because your dependent is required to file a tax return (has taxable income) then you will need to enter the amount as described in TurboTax. Please note though, that the instructions say, "add the amounts on line 4 and any tax exempt interest reported in the space to the left of line 2." You do not want to subtract the amount in line 2.