[Syla Delaney]

If it is a 'branch' after the end of the story, it gets cut off, regardless of it's state of being.

Branches are only cut off on their direct end points, that's when they stop, and time doesn't flow beyond that end point. Anything branching off before that end point flows on until they reach THEIR respected end points, and then are cut off, etc. etc. The end point is the exact moment the universe is intended to carry out. So in vague musings, it ends when it reaches the end of that vague musing. In full fledged ideas, it ends upon the designed finish.

I might make a flowchart or diagram, I think better in pictures.

[Peaceful_Chaos]

So time has stopped in one section of the same existence but keeps on going in another even though they're in the same existence?

[Syla Delaney]

Not quite, they are no longer the same existence once a branch occurs.
It's a parallel universe, living by its own new set of rules.
So it really depends on which branch is cut that determines if the other continues.
If its the main branch, and it's cut at a point in time BEFORE the other branch was created, the other branch will end up ceasing to exist.
If it's the shoot-off branch, it, and all of its shoot off branches after the cut-off point, will be cut off, and have no effect whatsoever on the main branch.

[Peaceful_Chaos]

But what if there are 2 stories going on in the same branch at the same time and one ends before the other

[Syla Delaney]

All branches are centered around a single story.
There might be other people living their lives, and such. And a branch might be complicated, but its main focus is on a single set of events that must occur. So, for instance, in our world, our reality, despite there being so many different lives and so many different events, there is only one absolute story that is 'planned' to happen. And once it reaches its critical point, ZIP.

So to answer your question, there's only one story per branch.
The branches might be exactly the same in all regards but something like a coin flip, or dropping a piece of paper, but once that single frivolous action occurs, it's over.

[Peaceful_Chaos]

What if a universe was set around one story but then some cutters broke in and added an entirely different story within the universe thus creating 2 stories

[Syla Delaney]

They would never add other stories, do to their incapability to do so.
XD
Once they are a full fledged cutter, they can no longer create, only remove.

[Peaceful_Chaos]

But what if one took their apprentice who wasn't fully a cutter yet who made a new story within a universe that already had a story

[Syla Delaney]

It would be akin to having a person that was part of the universe create a story.
It would become an offshoot of the universe.
What exactly do you think would happen, if it were theoretically possible though?

[Peaceful_Chaos]

I would think the concept of the old story ever happening would collapse, just how if you go back in time you change the future, if someone messes up what was originally meant to happen that concept would collapse and a new future set of events would be arranged in order to fit the new story that had been molded out of the old one. Like they broke a puzzle piece and re-wove it back together into a new puzzle.