The TurboTax calculation is correct. According to the Line 12 Wisconsin SB instructions on page 6, it is equal to the amount on Line 6 of Form 2441, but not more than $3,000 for one child or $6,000 for two or more children.
If you received $5,000 in benefits but paid $11,000 or more total for dependent care, then you would still get the full $6,000 subtraction from Wisconsin income.
