Death Wave question/explained.

Hi,

I need some help understanding the Death Wave UW. I've read the wiki to tried and understand it and I get most of it, but there's certain things I don't understand.

So Death Wave, the explanation when looking at it in-game says "Spawn 2 Effect Waves, then unleash a Death Wave which persists until dealing 15.12x Tower Damage (scales with all Crit)
Then in my case it continues to say:
Damage x3
Quantity 2
Cooldown 3m 0s.

My guess is that the blue/red bubble in the beginning is the "... which persists until dealing 15.12x Tower Damage...", essentially I read it as a reflective wall which reflects dmg back to enemies until it has dealth damage equal to 15.12x Tower Damage and then vanishes. Its "remaining damage before vanishing" is indicated by what is seen in this example screenshot.
The "pulses" you see later after the "wall" is gone is the 2 (in my case) effect waves mentioned?

DW Persistant Tower \"Damage\" stat.

This is all well and good. So its initial value is 15.12x Tower Damage meaning starting with a higher tower damage is good if you want this to "protect" you for longer? Which is a bit relevant to me in my HP Dissonant runs, since I'm eHP and don't really have a GC setup of any kind as I'm only currently trying to push to T8.

So what especially confuses me is that given the above understanding of how it should work. The number should only be able to go down - however in this run after I took the screenshot and while typing this post the value jumped gradually to 80q, what makes this happen? Essentially I'm wondering what levers I potentially can pull and turn to make it live longer, because something is making it last longer / "regenerating"?

For reference I don't have any UW+ or card masteries or similar - just in case any of those changes something.

Thank in advance for any help you can provide.