Dumb question ... why 1, 3, 5, for price breaks on Avast?

Sorry for being a noob on this board. I tried a google search, a forum search, just couldn’t find the answer.

I bought a three pack license for Avast, but now I have a fourth computer. It came with Norton (30-day?), so I am ok for now, but I would really like to stick to just one brand. Yes I could just install Avast free, but subscribe to the notion a company can’t make a living giving away software for free. But I don’t want to pay for a fifth license that I will not use.

Just get 1 license for that system or submit a ticket to avast and ask if they can give you the 4th license for the same price (per system) you have paid for the other 3.
Or ask avast if they are willing to convert the license to 5 systems.