Hello,
All download, upload and other client hotspot client information can be found by navigating Services > Hotspot > Statistics.
Realtime traffic can be found in Manage window. Go to Services > Hotspot. The Manage button will be located next to your hotspot instance.
If your device fails to show any statistics I would recommend checking if you are using the latest firmware version, update it if you are not, and try to reboot the router.
Regards.