Your 10 port USB hub (and other devices) may actually contain multiple USB hubs in series internally.
USB hubs are often built into equipment such as computers, keyboards,monitors, or printers. When such a device has many USB ports, they allusually stem from one or two internal USB hubs rather than each porthaving independent USB circuitry.
As stated, the USB spec allows 127 devices to be connected through a single port. However, the USB spec only allows hubs five levels deep, or seven if including both the end device and the root device (the onboard controller itself).
A Technical Introduction to USB 2.0 - USB.org (PDF)
A newly attached hub will be assigned its unique address, and hubs maybe cascaded up to five levels deep.
Interoperability Testing with USB Type C - USB.org (PDF)
"Contains devices behind 5 levels of nested hubs – the maximumallowed"
