Add calculations to category groups in Numbers on Mac
For each group or subgroup in a categorised table, you can add a function (a predefined calculation such as sum, count or average) to summarise the data in any column. For example, in a table with shirt sales data categorised by month, you could add a function to count the number of shirts sold each month. You can add these functions to the summary row in each category in your table.
Add a function to a summary row cell
You can add a calculation, such as count, subtotal or average, for any column of data in any group’s summary row. The same calculation is automatically added to all groups at the same level in the category’s hierarchy.
Click an empty cell in the summary row, click
, then choose a function.A label row appears above the summary row. These labels can’t be edited, but you can change their text style and hide them.
You can also sort groups by summary row values. See Alphabetise or sort table data in Numbers on Mac.
Remove a function from a summary row cell
Click the cell in the summary row with the function you want to remove, click
, then choose No Summary.
Show or hide the label row
A label row is an optional row located above a summary row. It shows the name of the category and for any cell with a function added, the name of the function (count, subtotal, average and so on).
Move the pointer over the empty square to the left of the row, click the arrow that appears, then choose Show Label Row or Hide Label Row.
You can also chart the results of the calculations in a summary row column. Select the column containing the summary calculations you want to chart, click 
in the toolbar, then select a chart type.