In compacted groups, N sizes aren't visible unless you press the triangles next to child elements.
However there is a way to show an N size for a parent group, (e.g. Q2), by telling it where to source an N size from.
1. In Q2's context menu choose "More properties...". From there, change type from "empty" to "default.
2. Choose a child element from which to get the N size. Put the child element's key into field.
3. Go back to the group's context menu and choose "Statistics...". Uncheck all except "Basis".
After making the changes above, Q2 will display an N size in the parent element.