Federal Tax due amount after adding SS benefit

I am surprised at the big change of federal taxes due after I add my SS benefit.

After entering income totaling $66,791.00 I owed $618.00 federal tax.

After adding $28,658.00 Social Security benefit my federal tax due is now $5,975.00.

I have reviewed various internet sites to find the answer for the big change but have

not found any good answers. Could the coding be wrong within turbo tax?