My review error comes up with this and i don't understand? The Nova Scotia Equity Tax Credit amounts you are requesting to carryback are greater than your unused credits.

If the amount of your current-year claim (line 6) is less than the total credit available (line 3) and you want to claim a carryback of the unused credit or calculate the amounts available to carry forward to future years.
The carry-back provisions allow you to apply unused credits against your Nova Scotia tax for the three previous tax years.

The credit you apply cannot be more than your Nova Scotia tax for that year. The total of the credit you carry back to a previous year, plus any credit you have already claimed in that year, cannot be more than $17,500.