Answer:
When applying an axial offset from members to the adjoining member, the outer edge of the second member is extended until it intersects the center line of the member to be reduced. This intersection point is the new member end point.
For members adjoining each other at an angle, this can be applied up to an angle of 135°. As of an angle greater than 135°, the cross-section is no longer reduced.
If two members adjoin each other, with the eccentricity assigned to both, the eccentricity is only modeled on one member to avoid a cyclic dependency.