A dumb question from a newbie

So my wife loves to cook and, as such, has a pretty large collection of knives. Probably 15 or so she uses regularly. I want to try and sharpen them for her, so I got a set of Shaptons (320, 1000, and 5000) and have been having okayish results with some less expensive knives but I’m struggling with identifying angle. Like I can use a sharpie on the edge to trial and error it, but I always see folks saying they put like a very specific angle (12, 13, etc) on their knives and I can only really ballpark… How exactly do you guys actually identify what angle to hold the blade at when sharpening? I can basically get and hold a consistent angle well enough, but I have no idea if it’s the correct angle. I just ordered some wedges to get a rough idea of what each angle “feels” like, so maybe that will help, but I would love to hear what the experts here do.

Thank you!