1. The table's mins divide straight line distance by the speed of light. This gives you the time it takes for light to travel in a straight line from, say, London to New York. However, your "real latencies" are roundtrip ("ping") latencies. Thus, you need to multiply all the theoretical latencies by two.
2. Data does not travel through a fiber optic cable at the speed of light. This is because light actually bends around the cable when transmitted. These are called cosine losses, and mean the light travels roughly 5/3 the actual cable distance. So, multiply again by 5/3. (This is why HFT firms use microwave links for long distances.)
If you multiply the theoretical maxes by 3.33, you'll see that they're very close to the actual latencies you're observing. New York -> London becomes 62.7 ms optimal, so you're only 13% slower than the theoretical max.
Here on the west coast, I typically see within 10% of the theoretical min for data going over the Seattle -> Japan submarine cables.