In this case, you really want to have the hour as a Pivot table field. To do this, create an extra column in the source data and use the function HOUR on the OpenDateTime column. You can then create the Pivot table with the Day of the Week on one axis and the Hour on the other with the Count of tickets as the value.
In order to get the average number of tickets per hour per day, you can either create a calculation table using the body and totals of the pivot table, or recreate the Pivot table with the value 1 against each ticket so that the average option can be chosen and not applied to the actual ticket reference number.
