Messaging Gateway Combined Message Queue is too Large

We are on version  10.0.2.

For the first time I received a notification about the messaging queue being too large. Below is the message I received.  

======================= ALERT NOTIFICATION ================================              

The combined message queue for the following Scanners is larger than 102400 KB

Scanner                  Combined Message Queue Size (MB)
---------------------------------------------------------------------------
SMG                      293.1
 

 I have checked the messaging queue and searched the filter with the below criteria:

 Host: SMG

 Queue: Delivery

 Route: All

 List: All

And I only see one message in the queue with size 22409.

What is the recommended action to take when receiving this message?