How to do station equalities in InRoads Power Survey SS2

I am currently attempting to station the following:

I was at the point of putting in the stations when I was made aware that there were station equalities that needed to be addressed. At the intersection of the green and blue lines there are two stations: P.O.T. STA. 18+81.85 NORTH AVENUE (the blue line traveling west to east) = P.O.T. STA. 50+00.00 ARCH STREET (the green traveling north to south). 

As I understand it, to address the station equalities, and to station the blue line to start) I would have to measure the distance from the end of the blue line to the intersection of the green and blue lines, and then subtract that number from the blue line station. The resulting number would be the station at the start of the line. 

Still new to alignments and stationing, I put that number in to the stationing dialogue box:

...and hit apply.

Not quite the result I thought it would be.

I have a couple of sources but nothing that explains what I should have done. I have a vague idea that STA 18+81.85 might need to go into the Ahead Station, but I've nothing to confirm that.

Anyway, is there a better definition of "station equalities" than what I'm using, and what *should* I be doing in order to get the stationing correct. I have eight of these, so if I get the first one, one would think the rest should fall into place.

thanks!