Based on my understanding i will give my inputs.
For example if you have a resource name called “Teller” who is working on a job process. Teller will click around 100 clicks to complete a single job process for a customer in manual way. On daily basis Teller will process around 20 to 25 customers. That means Teller is going to conduct around 2000 to 2500 clicks on daily basis.
Now if you create a bot script and try to mimic same click operations in a machine that bot will conduct same operations for 20-25 customers then you got a bot to contribute instead of a human effort in 8 hours of a working day.
Now you want to serve your clients more faster than usual time. You just increase machines to 5 and run same bot in 5 machines. Now you can serve 5*25= 125 customers in 8H of working time with out any manual effort.
Hope you understand the calculation how many number of bots you need based on your task.