PivotTabe - Summary row - count and average

[zino1]

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

[TABLE="width: 381"]
<tbody>[TR]
[TD]Row Labels[/TD]
[TD]Sum of ga:metric9[/TD]
[TD]Count of garoductSku[/TD]
[TD]Average per ID[/TD]
[/TR]
[TR]
[TD]19-Sep[/TD]
[TD="align: right"]94[/TD]
[TD="align: right"]4[/TD]
[TD="align: right"]2[/TD]
[/TR]
[TR]
[TD]1139194788.1474319040[/TD]
[TD="align: right"]47[/TD]
[TD="align: right"]2[/TD]
[TD="align: right"]-[/TD]
[/TR]
[TR]
[TD]1139194788.1474319041[/TD]
[TD="align: right"]47[/TD]
[TD="align: right"]2[/TD]
[TD="align: right"]-[/TD]
[/TR]
[TR]
[TD]20-Sep[/TD]
[TD="align: right"]39.55[/TD]
[TD="align: right"]29[/TD]
[TD="align: right"][/TD]
[/TR]
[TR]
[TD]1191911439.1474393408[/TD]
[TD="align: right"]22.8[/TD]
[TD="align: right"]1[/TD]
[TD="align: right"][/TD]
[/TR]
</tbody>[/TABLE]

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