For natural numbers less than 1000, why should 0 be less than or equal to x less than 1000 in the set composed of odd numbers

For natural numbers less than 1000, why should 0 be less than or equal to x less than 1000 in the set composed of odd numbers

The minimum odd number is 1, and the maximum odd number less than 1000 is 999, so 0 is less than or equal to X and less than 1000