Hamstovitch

Just a little question. But it is impossible to make trainers have shiny pokemon in gen 6 right? I've been looking for it but i am unable to find where. I was able to when i did a UsUm one so i thought that maybe it was because pokemon in OrAs(Gen 6) were never coded to be able to be shiny.

So i was wondering what it means when i go to edit the IVs of trainers pokemon but instead of the traditional 31 in a stat thingy it gives me a slider that goes from 1 to 255. If it is purposefully done so then i'd just like to know how to actually use this function and/or what it actually does. A gif that shows what i am talking about. https://gyazo.com/542d47d126d3a0659b8758409afa630d