HFSS Lumped port direction

I designed a prob fed microstrip patch antenna and used Lumped port but I dont know which direction will I draw the integration line for the port? When I changed the direction (x or y axis) the results were change. could anybody help me?

Rule of thumb: to set one end of the integration line on the edge of the upper radiator patch, and the other on the edge of the lower gnd plane.

I did the integration line started from the gnd plane to upper pathc. I hope it is true.