Custom Object Program Canvas - Pending Members

I have been looking for documentation to define what Pending Members means, as there is strange behaviors happening on a custom object program canvas that I cannot account for. I suspect it may have to do with Pending Members (I saw the report for it on the program canvas). As far as I can tell, the pending members does not have anything to do with listener steps, as the numbers for the pending members do not match the numbers for the custom object service record. So if anyone knows what Pending Members means on a custom object program canvas, that