The difference between the 1st and 2nd digits is divided into 7 portions

The difference between the 1st and 2nd digit of the lottery numbers is divided into 7 parts.

Part 1: 1 - 3

Part 2: 4 - 6

Part 3: 7 - 9

Part 4: 10 - 12

Part 5: 13 - 15

Part 6: 16 - 18

Part 7: 19 - 21