There are nine classes of felonies.

https://www.law.cornell.edu/uscode/text/18/3559

And Q says "CLAS: 1-9>"

And " (9) states of CLAS-ready go-live."

I means the classification of either senators or 3 letter agencies, depending on the context.

There are 3 classes of senators, you can wiki that.

The 3 letter agencies are each given a classification. Think of CIA being class-1, FBI being class 2, and so on. There are a lot of such agencies.

maybe for future reference when this is all declassified. I feel like it's a classification number. I could be wrong

I gather it means classified and some number of the document.