Can you please provide your packaged workbook?
I took a stab at it, but I fear it may not work for your setup.
I made a dual axis map, one axis with Color Filter the other without.
It appears that the Color shelf takes precedence for getting aggregated
in the tooltip. When I moved the non-colored one to the leftmost position
on the Rows shelf, it seemed to aggregate on # of Machines.
However, because of the dual axis, I worry that I may be double counting.
I couldn't immediately tell.
Anyways, maybe this can give an idea.
Please see workbook v2018.1 attached in the Forum Thread.
There seem to be some Ideas about this tooltip, but not specifically your usecase.
May want to search and submit the idea if it's not there:
278679mapselection.twbx 267.9 KB
Thank you! The solution is not ideal, but it works!
interestingly enough it seems to double count how many items are selected, but not "# of Machines".
the idea threads posted are related, but a little different. I may make an idea thread as well.