My experience with a trip I did in Dec with my new CapOne card was similar to mahasamatman, my rates were lower than what I was expecting. My guess is, and looking at a graph on Oanda over the past 30 days confirms this is possible, that the rate fluctuated about 1.5% overnight and the difference you are seeing is the result of the rate they used being the difference of either the posting date vs the transaction date.