Sometimes your state refund isn't the same as expected because the tax agency may adjust credits or apply debts after you file.
The amount you see is based on the info you entered, but the IRS makes the final decision. If they make any changes, you should get a letter explaining why.
To see how this works, click the link below:
Why is my refund lower than the amount shown in TurboTax?
In regard to your Federal payment plan, if it has not been processed yet, you should reach out to the IRS directly or set it up online.