2210 Line 8 Source - Prior Year's Tax

Form 2210 is reporting a Line 8 which is $3,335 higher than expected for my Prior Year's Tax. When looking at the "Data Source" Carryover Wks is opened and box 6 is highlighted with the expected amount, which does not match line 8. Is there a calculation on the Prior Year's Tax for a 2210 Underpayment or should it just be the same as 1040 Line 24 - Total Tax?