Taxes on Inherited IRA Withdrawal

I inherited an IRA from a parent this year and decided to cash it out rather than stretch out the RMDs since it wasn't a crazy amount. The advisor at the institution withheld appropriate amounts for both federal and state. After entering my 1099-R into Turbo Tax, a percentage of the withdrawal at exactly my tax bracket is being subtracted from my potential return amount despite entering the proper fed/state withheld amounts. The software must just do this as a precaution, right? There's no way such a ridiculous amount of tax is still owed on this.

 

Been doing some research on this but can't find an explanation.