Kinda weird that there is no mention of their fruiting process.
The "traditional" approach is to let the beer ferment out and age until you're happy with it and then add fruit. Let the fruit sit until you're happy with it and then package. Aging on fruit can be anywhere from a few weeks to many months. I've aged sour beer for an entire year on fruit. The rule of thumb is the shorter contact time (weeks) will elicit a fresher fruit flavor while more time will yield more of a fermented fruit flavor. There isn't a right answer, it's more about making sure the fruit fully fermented out (which sometimes can take a couple months) and when you like the flavor.
A less traditional approach is to add fruit 6-9 months after brewing and let the beer continue to mature while it's also working through the fruit for another 3-6 months. The downside is sour beer doesn't necessarily work on a guaranteed timetable so you may be happy with the fruit character and less so with the underlying beer character but once the fruit is there you can't take the fruit flavor back out.
Fruit volume is pretty well all over the map, too. The "traditional" volume for raspberries is 8-16 oz/gal but most modern fruited sours are more in the range of 1-3 lb/gal. Personally I want to taste the beer and the fruit so I usually use 12oz/gal for berries (for 3-4 months). If I wanted to taste fruit wine I'd just make fruit wine, but I get that I am in the minority.
