Please correct me if am wrong,
You need a total count in the same panel of a pie chart?
It can be done using single value and pie chart in the same panel, here you need to use post process search picking total for single value and other values for pie chart.
..|eventstats sum(count) as Total|table Source,count,Total
Dependent Search 1 (For Pie chart)
Dependent Search 2 (For Single Value)
stats values(Total) as Total|table Total
If you don't want you use single value.
Use Java Script to find a total and set a token to display in the html tag inside a panel.
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