Here are the report parameters:

What 

1. Solved Tickets
2. First Reply Time

How

1. Week / Month / Year, etc. (whatever you want)

Filter

1. Ticket Id where # MY TAG is equal to 1
    

This is a custom metric, the MAQL of which is:   SELECT  # Tickets WHERE  Tag= MY_TAG

(note that mine uses "engineering" as the tag, but that's just the value I was interested in for my own report).