Alerts are not a traditional association to objects. It is a database query that is run and will return anyone that matches the logic. Sorry for bad analogy: Shouting into a large room, "who is over 90% CPU", whoever raises their hand is the winner. It does this every (1 minute by default) in a 'are we there yet, are we there yet' fashion.
The number that populates at the end of the alert builder UI is a helper that lets you know how many would trigger at that moment in time if you hit submit, not the total number of applicable/associated objects.
Can you share some screenshots of what your doing? Is the alert your crafting expected to fire the moment the alert is generated (ex: making a cpu alert, and you have a switch with 100% at that moment).