In my case box 17600 is $40 which is greater than box 68140 which currently is at $0. Thus the error.
On Schedule 3, Period 1 near box 17600 has all the losses for the year. Period 2 only includes the $40 of capital gains from the T3's.
Not sure if that helps all that much from my perspective but maybe someone else on here might be able to use this information.
