I, I have a diagram where I show flow of information from one to another using a connector. I am using a one sided arrow to show one sided flow and double sided arrow to illustrate both side flow. Now, I also want to show how much unit is flowing from shape A to Shape B (and how much from Shape B to Shape A). I was trying to do this with the label of the connector. I was putting a label (of the connector) something like "←3 units,  2 units→" to show data flow of 3 units from Shape B to A and flow of 2 unit from Shape A to Shape B. But the problem is that when using auto layout, Nevron arranges everything and Shape B and Shape A might be aligned in such way that the connector is reversed in which case it would seem that the data is reversed (i.e. 3 units from from A->B rather than B->A). How can I set it so that my test start point is always located from the port.From side.

It may also be possible to illustrate the same information if I could put labels or texts on Arrowheads which I have not found any way to achieve it.

Any help is appreciated.