I got $3,300 in child tax credit in 2021 but I don't think that's what the letter stated i would receive, how do i fix it?

For the majority of taxpayers, the advance payments total in Lettler6419 will match the total in their online account. 

If the advance payments total differs between your Letter 6419 and your online account, rely on the total in your online account.

Your online account has the most current advance payment information. Do not rely on the Child Tax Credit Update Portal or Tax Transcripts for the advance payments total.

When preparing your tax return using TurboTax, enter the actual amount reported in your online account instead of the amount reported in Letter 6419. 

Keep Letter 6419 for your tax records.

Follow this link to sign in to your account on the IRS website.