what determines what page you view when you click an ISO?

[xyzzy]

as you probably know, if someone has >200 posts in a thread, their ISO is paginated into 200 post pages. the weird thing is, when you click on that person's ISO from a post they've made, the page it goes to seems to be random. what determines that behavior? is there a specific reason it doesn't just automatically go to a particular page (either the first one, last one, or the one that the selected post is on)?

this is in the help subforum because it's not really relevant anywhere else but I also don't need help with anything, but, like, listen, I picked the best one I could