PivotTabe - Summary row - count and average

[zino1]

I have a pivot table, built from a table of product adds on an ecommerce site:

Row Labels	Sum of ga:metric9	Count of garoductSku	Average per ID
19-Sep	94	4	2
1139194788.1474319040	47	2	-
1139194788.1474319041	47	2	-
20-Sep	39.55	29
1191911439.1474393408	22.8	1

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How do I get one more column, that gets the average items per ID?

In other words can I create calculations based on calculated pivot table data (sum(count)/totalIdsForDay)?

Two possible solutions I considered were to create another pivot table based on this one, or to copy the data as values? But can it be done simpler?

Thanks