Hi Pavel,
Try the following, it worked for me during a test.
You have a Custom Dashboard with the following reports showing;
Protocol Summary, Department then Policy, Top Shares at Risk, Target Summary, Incident - All & Policy Summary
You'll need to edit each report to remove Info incidents, for instance,
"Protocol Summary" is under Incidents > Network > Network Reports > Protocol Summary
Select the report, uncheck the Info box on the top right and "Save As" name the new Report as "Protocol Summary HML" (as an example)
Go back to your Custom Dashboard and select Customize. change one of the drop downs from "Protocol Summary" to "Protocol Summary HML"
Save and check the result, the graph should now show no Info incidents. You'll then need to repeat this for each Report that appears in the Dashboard.
David