NetBackup licensing is a horrible mess. It's almost impossible for you to know if you are licensed for everything you're using or even to know what you're licensed for. This works both for and against you - you have the flexibility that the product doesn't break when you exceed your license limits but you may not be in compliance with your license agreements or you may be over-licensed and paying more than you should be.
We have installed licenses that have verbiage like "see the paper certificate for the actual usage limits". We have VMware guest licensing that changed over the years.
You will need to know a LOT about your environment - what clients you are backing up, what their tiers are, and which are virtual and which are physical. You then need to dig up your entire order history for your products and if you don't have it but have been a long-time customer, you'll find that Symantec may not be able to help either because of their Veritas acquisition. This gets further complicated if you bought from resellers. If you do have all of the data, you can then contact Symantec and work with an SE to do a license audit using some tools that they have (previously known as Xenon but I think the name has changed again).
Symantec product management knows about how ugly it is and has been working to make it better but I don't know if they'll ever get there since the problem is really, really, really hard.
