Tolerances are like margins of error. As the error range goes down, the exactness of the specification goes up. Or as the others said, the precision.

If it makes you feel any better, I have to pause for a beat any time I try to put an adjective in front of 'tolerances' to make sure I don't sound like a dope.

Lower tolerance numbers, higher precision

It’s kind of counter-intuitive, you’d expect lower tolerance to mean the tolerance for deviations is lower, or higher precision

In practice, “high tolerance” is used to mean “tight tolerance”. “Tight” is more commonly heard, at least in the US.