Sum, Count, Avg, Min, Max button will add another column where you can see the sum, count, average, cumulative sum, min, max or median value for one of the columns you choose.
Go ahead and click on the Add Transform, then select
Sum, Count, Avg, Min, Maxbutton.
This will bring up a window where you can add some sort of aggregation to a column. First, choose your aggregation.
Once you've done that, you will see another field where you can choose what column to apply that to.
If you'd like to add multiple columns with various aggregations, just press the blue Add Aggregation button and repeat the steps above.