Math question w/ niagara positioning

I found the problem, but it’s very confusing.

When I first set the “Progress” at my particle spawn, that module got called every times I set the switch in the level so I keep setting the “Progress” to the initial number. That’s why it jumped to position when switches.

But that is not what I expected particle spawn to do. I thought anything in particle spawn only ran once when … well … particle spawns.

Now I have to use the switch to reverse the number for it to reverse, which is so weird…does it intended to work this way?