As per the documentation of QueueCountAlert:
Number of messages on this item's queue needed to trigger an Alert message to be sent. Note that no further alerts will be sent unless the number of messages on the queue drops below 80% of this number and then rises again to this number.
Note that this alert will be sent even if AlertOnError is False.
Zero means no alerts of this type will be sent.
Now, the question is,
If QueueCountAlert is set to 10, and the queue size become 11 we will be getting email once.