What is the average statistics on calls in those. support?

Question

Helpdesk

Are there global standards or best practices for the number of calls to those. support, average call time, calculation of the required number of employees (except for the Erlang formula), etc.?
Interested in information for call-centers and for the first, second, n-x support lines.
Any articles, links, etc. Thank you.
UPD. The question is whether there are such statistics or recommendations on the load on the technical department. support?
For example, on average, one call center employee makes 50 calls daily, on average it takes 2 hours to process a request on the second line, and 3 people are displayed to process 300 calls, 500 letters and 1000 chats according to some formula.

Answer 1

I don’t know how much it will help, but I once read about best practices here : https://www.intercom.com/books/customer-support ). If I remember correctly, it was briefly described there about the calculation of the number of employees, but to see what the department’s time is spent on and what to optimize from processes (time zones, some types of appeal), it was described using examples.