Guys, you are missing the point a bit. He's putting a dimpled part in that countersink. Judging by that, I'd say he's only a little deep and probably not enough to worry about.
Med322, I go a little deeper with countersinks that will hold dimples but I only use about half the extra depth you used. If you countersink until the dimpled part fits completely flush before riveting, you've gone too far. The countersink has a sharp edge while the dimple has a radius. When you countersink enough to let the unriveted part fit flush, you have taken enough material for the radius to fit in but now there is a gap between the countersink and dimple. It's small and won't be a problem for the occasional rivet, so if this is the only one you've done this deep, then just move on.
The actual depth you want is about halfway between rivet flush and what your picture shows. It's hard to be more exact; there are people here who will give you measurements but it varies by the thickness of the dimpled material. Experience is your best teacher. Try testing on some scrap (you can get cheap bar stock at Home Depot and Van's supplies a trim bundle for the thinner material). What you want is just enough so that - after riveting - the dimpled material sits flush to the material underneath. What should happen if you countersink a little less deeply is that the act of riveting will cause the countersink and rivet to act as dimpling dies and sharpen the dimple's edge radius to match the countersink, bringing the parts together.
