What do you mean by "estimated"? Where did you see an estimate of your refund? Your actual federal refund is the amount on line 35a of Form 1040 in the tax return that you filed. That is not an estimate. If you chose the option to have TurboTax fees taken out of your federal refund, then your refund will be reduced by the amount of the TurboTax fees plus a processing fee.
The IRS might have reduced your federal refund. If so, they will send you a letter explaining what they changed. You should get the letter 2 or 3 weeks after you received the federal refund.
