How does a lottery number from 1972 make any difference to Bush's 1968 service? The lottery started in 1972, my senior year at Univ of Wisconsin.
No.
The lottery began in 1969, it ended in 1972. Look here. The prime eligibility year was at age 19. I don't believe the lottery applied to Bush, who was born in 1946.
If he was born in 1946, then the 1969 draft would have included his year group because it was a broad year group -- about 1945 to 1950 (18.5 to 26 years old).
It was a moot point because he was already in service.