In case anyone finds this thread via search.
You can exclude a Request error by first clicking the top error so it navigates to that specific Request error page. Expand the detection rule navigation box and click on Edit or Create detection rules for this error pattern.
Then Edit or Create the detection rule and uncheck the checkbox Capture this error.
You can also do this straight from the Web application settings. In the Application navigation select Errors and then click on the button Add request error rule.