An example that [in my opinion] is not obvious for calculation:
A or B where one part in Unknown.
(unknown) or (true) and trigger goes to the problem state
but
(unknown) or (false) and trigger is in unknown state (problem is still active)
Add some examples of how to do this: use count\nodata function to make A (unknown) part true or false

In A and B calculation, when it is (unknown) and (true) trigger will go to unknown state straightway (which is 'easier')

Also if you don't have access to the Configuration menu iе can be hard to guess why after fixing the problem (in reality) it is still on the Zabbix dashboard. Maybe add a note for that too

Regards, Elina