A Minor 6th can be though of as a Major 6th that has been lowered by a half step.
By themselves, Minor 6ths tend to have a sad sound.
A Minor 6th is equivalent to 8 semitones.
Because it is a large interval, it is helpful to think of a nearby anchor point, rather than counting your way through all six degrees of the scale.
Always use a Perfect 5th for reference, then go up a half step.