active directory - Correct licensing if users have multiple AD accounts

When licensing User CALS for Windows Server, I have following problem (or question):

Given you have 30 employees in your domain. 5 of them are administrators.
Each of these administrator has two domain accounts, one for working, with almost normal permissions, and one account with domain admin permissions, for logging in into servers and workstations. This helps distinguishing who was responsible for a software installation, reboot etc.

Now, do I need to buy 35 licenses for those 30 physical employees because I have 35 user accounts or is it enough to buy one user CAL per (physical) admin?

Same question appears for a special backup user which is used by backup scripts (=no physical user) to tranfer files to our file pool.

I already checked Active Directory Licensing but it doesn't completely cover my question.