The 600 is probably for the 2nd stimulus not the 3rd one. The 3rd one is $1,400 per person.
Did you get the first and second stimulus checks? Only the first 2 rounds go on your 2020 tax return. Not the 3rd one. Did you get the second one after you filed? You had to enter what you already got into the right 2 boxes or Turbo Tax gave it to you again. The IRS knows they already sent it to you. Line 30 is only if you qualify more for the 1st and 2nd ones.
