Create Association Records GP tool buggy / invalid results

[LizAbbey]

System Details: Pro3.1, water distribution foundation v1.3, coordinate system New Zealand Transverse Mercator, units: metres

I'm getting unexpected associations using B_Rules table and Create Association Records GP tool.

I have generated some test data inside a foundation water distribution asset package consisting of service connections and service meters. The service meters are offset from the connection points in distances from <1m, <5m and <10m.

In this attempt, I have nominated 1 as the "Distance for associations" in the B_Rules table. I would expect that only meters within 1 m of a service connection would have an association record generated.

Below is a screengrab of my B_Rules table, noting that there are only distances nominated for meter to service connection, and not meter to meter. The rest of the table's distance values are <Null>:

Below is a screengrab of my meters and service connections. Red circles are 1 m buffers around the service connections that I'm testing. Three meters are within a red circle and I expect them to have associations generated when I run the Create Association Records GP tool:

The tool runs successfully, but too many associations are generated. In addition to the three I expected (green circles), an additional four (red circles) were generated that connect meters with other meters:

One pattern I note is that meters that are not connected to anything are >5m away from the next device, otherwise this looks random. 

To prevent the association records from being generated I was able to put in a distance of -1 for all the undesirable meter-to-meter connectivity (highlighted rows below):

Is this a bug? If not, can anyone point me towards additional documentation on how this distance field is supposed to work?

Thanks

[MikeMillerGIS · Accepted solution]

The embedded tool help has the following info, which matches what you are seeing:

To define distance, add/populate a double field in the B_Rules table, "association_distance". This value will be used as a search tolerance for features that match the rule.
If this field does not exist, or the values are null, then a default of 5 units will be used.
Rows with a negative association_distance will be excluded from processing.

I added an issue to get this added to the web help.  

[LizAbbey]

Thanks for the tip - I searched high and low for this info on the Esri pages and didn't think to hit the little "?" within the tool parameters box.