When counting hubs, you assume that every individual box/device has only one hub. This assumption is likely untrue.
To begin, the 10-port "amazon hub" definitely has at least two hubs in chain, because single hubs are not manufactured with 10 ports, 7-port maximum [see this explanation].
Then the Dell monitor has also some special design - it has TWO UPSTREAM ports. What is its internal architecture, who knows.
The "surface dock" is also a suspect for having more than one USB hub in the chain. And I don't know if the "surface" uses extra internal hub for whatever reason.
To get the actual idea how many hubs are there in the chain and what/how all things are connected, use USBTreeView.exe on the Surface side. I am sure the Surface got the chain right, and you do have more than 5 hubs in the chain.
Addition: USB standard allows for 127 devices per one root controller, it doesn't mean that they are "daisy chained", just total of 127. In fact, if we discount hubs as functional USB devices, the total number of useful devices comes down to 102, since you would need 17 7-port hubs to accommodate the devices, in three-tier configuration, and each hub will take one address out of available space.
