Determining force out on appeal 5.5.B(1)
 

I could use a little help.

I've always been a bit confused on what this statement means regarding determining force outs on appeal:

"On an appeal play, the force out is determined when the appeal is made,
not when the infraction occurred".

What exactly does that statement mean?

It means that if a runner from first misses second on the way to third and then the batter-runner is thrown out that the miss at second is a timing play so any runs that score on the play could count. Whereas if the runner is safe at first, then the out at second is a force out and runs might not count.

More formally:
Bases loaded. B4 singles to right and on the misplay all runners advance home. B4 is a) thrown out at second trying to advance for the second out. b) safe at second with two outs before he it. In both a and b, R3 missed second base.
In a) on appeal R3 is out R1 and R2's run's count. In b) on appeal R3 is out, no runs score because R3 was still forced to advance to second.