Sorry, is this a question about those numbers?
533MHz is one of the common clock rates. The 10600 is not in MHz but some bytes per second over the bus connection.
Both Crucial and Kingston have memory selection tools to get the right sticks. They may offer faster parts than are required for a very simple reason. As production techniques improve the speed goes up. And since there is no reason to keep speeds low, and higher speed parts will work fine, the lower speed stock is consumed and may never be found again.