If you look at a number line like we learned in primary-school maths class, it's easy to see that a "30-year-old" would be in the 30-34 range, not the 28-30 range.
If you're exactly 30, just wait a few seconds, and then vote.
Ages are natural numbers by convention, nobody is ever 30.00000001 years old. 28-30 is another way of saying 28<=n<=30, not 28<n<30 nor 28<n<=30.
