Find number abc

One of the regular foursome was sick, so a new member named George filled in. He was very good and pleasant company so they asked him to join them again the following Sunday. "9:30 okay?"
George said, "Fine, but I may be about ten minutes late. Wait for me."
The following Sunday George showed up right on time. Not only that he played left-handed and beat them.
They agreed to meet the following Sunday at 9:30. George again said, "Okay, but I may be about ten minutes late. Wait for me."
The next Sunday there was George, punctual to the dot. This time he played right-handed and beat them again.
"Okay, for 9:30 next Sunday?" one of the foursome asked.
George said, "Sure, but wait for me if I'm ten minutes late."
Another golfer jumped in. "Wait a minute. You always say you may be ten minutes late. But you're always right on time and you beat us whether you play right or left handed."
George said, "Well, that's true. I'm superstitious. If I wake up and my wife is sleeping on her right side, I play right-handed. If she's sleeping on her left side, I play left-handed."
"What if she's lying on her back?"
George said, "That's when I'm ten minutes late!"