How to perform this?

Technical Support Modeling
1

I’d like to perform the change shown in yellow in the two images below but I don’t know how to. Edge befor spinning
After spinning

2

Select the edge, open the edge menu (Ctrl+E) and use “Rotate edge CCW”

3

Or you could dissolve the edge and then add an edge with the knife tool.

4

I did that and this the way it behaved:

This is how it was executed
This is how it was executed503×501 56.6 KB

5

Ain’t that the change you wanted? (for the opposite side you would use rotate cw instead of ccw (clockwise instead of counter-clockwise)