question

Your question has been answered already in two of the answers below.

@Sachin T, you can still use the answers that were given by Anthony and Zixuan. In fact, Zixuan's answer uses similar code to the Activity Stat dropdown option from Anthony's answer. Even with an internal list, you still have access to the list's stats using that option/code.

There's probably still a way to do it like in Matthew's answer, except content(), listentries(), and listbackorders() are deprecated now. You would instead use treenode.subnodes.length, List.entries(), and List.backOrders(), respectively. The tricky part would be getting a reference to the internal list in the List resource's tree. It's possible, but using getstat() and getactivity() are easier.