Ok Ram, you def have me in the right direction and I'm almost there. I understand the functions a little more clearly now, but still have a problem translasting it. I tried to bring it over more or less exactly, but without the wave functionality you built in yours, since mine is going to be more of a level system rather than waves. When doing that, It wouldn't wait between spawns, and it is spawning them infinitely.
I got into looking through tutorials of some of the functions, and I wonder would the repeat function be something that would work for me? In my mind, I want to take the system repeat function, tell it to repeat x amount of times, then I want it to spawn object with a random range delay, so I could do random (3, 5) and it would randomly spawn between every 3 to 5 seconds. Then lastly, I want to use your set frame option, to have it randomly choose which one to spawn from.
End result, game randomly selects spawn point every 3-5 seconds, spawns a unit, and repeats that function x amount of times. I'm going to mess with it a little longer before I call it a night.
Edit: So I messed around with it a bit longer, and I came up with something that to me logically should work perfect, but logic isnt winning here. Here is what I have
Condition: Repeat 10 times
Condition: Pick a random instance (spawn sprite selected)
Action: System wait 5*loopindex
Action: (Spawn sprite) spawn (Object sprite)
What I expected was for it to spawn the object 10 times, once every 5 seconds at a random spawn. What I got was it just spawning an infinite amount of objects at every spawn. I also tried your for command that you used, and ended up with the same result. I think I'm close, just missing something small I'm sure.