About 16.7 MKeys/s, 1 GKeys/min.
Let's say 2^24 Keys/s.
To compute 2 lists of 2^28 keys, it takes 2 * 2^4 seconds, about 30 seconds. That is the time it took to retrieve the key #57.
Have you tried to search a key in space of 10 quadrillion? How many hours you think it can finish that large space?