Hello Lgp,
Welcome to the community!
It is not really possible to provide the data usage per hour as the amount of data used during that time period depends on your activities while tethered to the laptop. Streaming video would use considerably more data than simply checking email during the same time frame.
You can use the Mobile Data Calculator to estimate your monthly data usage. You can also estimate your hourly usage here. While that webpage refers to broadband usage, it might provide an approximation of hourly mobile data usage.
You should note that a computer tethered to your Wifi-hotspot can use markedly more data than your mobile phone or device.
Hope this helps 
Cheers
Hey @lgp
Welcome to the Community
When you tether and use your cellphone as a modem to connect to internet on your laptop, the data usage will simply be deducted from your plan's existing data bucket.
Just a heads up that you need a plan with a minimum of 1 GB to be able to use tethering.
If ever you go over the data that comes with your plan, regular over usage charges will apply. You can check out your over usage rate through your online account under the plan's details.
I suggest that you monitor your data usage through My Account online and the App to stay in check of the usage and avoid going over.
Hope this helps, let us know if you need more info
