I'm going to have to disagree with Oxford Blue on this one:
The question as I have seen it is for a flight directly North from 5S to 5N and asks what is the expected drift of a DI.
For any such calculation the Earth rate is taken at the mid lat position, in this case 0N/S where Earth rate wander is zero. There is no transport wander to consider.
I agree that wander at 5S would be an increase of 1.3 degrees per hour, and at 5N it would decrease at the same rate, but that would not cause a total drift of 2.6 degrees. They would in effect cancel out.