You need to write Runnig total for count of YESs in Trial avaliable
* Right Click on Trial Avaliable field and select Insert > Running Total
* Select Field to summarize as Trail Avaliable field.
* Type of Summary should be Count
* In Evaluate section select Use a formula(X-2) write below logic
if (Trail Avaliable field) = "Yes" then True;
* Close the formula window
* In Reset section select On change of Group and select Group2
* Click on OK
* Then place the Running total field in Group Footer @