Click on the Advanced Events Icon, then on Reports.

Choose Event Report.

Fill out the prompts on the first tab to reflect the way you want to run the report.

Next, click on the Filter Tab and click on the three dots next to the Matter field (ellipse button).  You will then get a list of Matters available to select. Make sure your sort order is by Client-Matter Number (if not, click on the Client-Matter column heading to sort the column in the correct order). Highlight the first Client-Matter number in sequence that you want, hold down your Shift key, and select the last Client-Matter number in sequence. Once all are highlighted, you may right click and choose Mark Selected. This should place a check mark next to all the Client-Matters you have selected.  Click on the X to close out of the Look-Up.

The main tab you are on now should show one filter set. When you run the report, it will present only those events on the Client-Matters you have selected to be included on the report.