The properties in this category control how the contents of the Sub-Grid are sorted when displayed.
Default Sort Column
This optional property controls which Column field name to sort the Sub-Grid contents with. If left blank the first column will be the one used for sorting.
Sort Direction
If a default sort column is indicated in the web part properties for the Sub-Grid, you may designate whether to sort in ascending (default) or descending order.
Allow Dynamic Sorting
This optional property enables sorting of the Sub-Grid contents after the page loads by selecting the column heading.
Click on the header to display the sort icon: