Hey there, Aidan118! The hotspot service is capped at a certain amount of data. It does not throttle. Is not like your regular data that allows you to still use your data after the allowed amount per month. We apologize.
To my understanding, if you max out the data on hotspot, then you won't be able to use the hotspot at all until the beginning of the next billing cycle. As for data on your device, if you exceed the 35GB you "may" be deprioritized for the remainder of the cycle. In my personal experience, even after hitting the threshold, I have not seen any reduction in my data speeds, however it could just be that the network has never been congested enough at my location to trigger any slower data.