I have manually checked on the Management portal (Message View) and getting same or close count of messages with Enrico query. I have tried this for a day timeframe.

As a result of your query I'm getting a different value with respect to if I run the same time frame with Jeffery Drumm query. For e.g I'm getting a value of 52890 for both of your quries (same count). But if I use Jeffery query I am getting a total of 136,175

Thank you @Enrico Parisi 
:-)

distinct session ids

UPDATE: I had all the productions exported as .xml file and then opened the file in Notepad. With the help of ctrl F,  I was able to locate which component is using the desired class name. This is a very manual way of doing it and is good until the prod config remain the same. Working on and interested to get an automated process of running it every time by providing the class name and it pulls the info.

@David Hockenbroch Thank you for your response, but I still don't see which operations (for e.g) are utilizing the abc.test.cls.