On a left handed guitar the volume knob should rotate counter-clockwise to increase the volume. It's the same direction as on a right handed guitar - just mirrored.
I'm not sure any of my guitars have numbers on the knobs, and I certainly never look to see if they do. But I do care which way the knobs turn yes, I want all my guitars to be the same - I've never owned a guitar which operated in the opposite direction. They are set-up the way they are for a reason. If one of your guitars is operating in the opposite fashion to your other one, one of them is wired as if it was a right handed guitar - tis a simple fix if you have a soldering iron!
The issue is more in the range of the 'sweep'. On most left handed guitars all the manufacturer does it use right handed hardware and wire it backwards so that the pots operate in the direction they should
. Unfortunately this screws things up and what you'll find is that there is an abrupt and non-linear change in volume levels as you rotate the knob. For example if you have the volume completely off, turning it up to 2 or 3 will make minute changes and then all of a sudden above 3 it's just full volume with very very very little change all the way up to 10. If you used a proper left handed pot the change in volume would be smooth and gradual all the way up to ten. For a correct left handed pot you need what's called a reverse-log pot. This pot has the taper running in the opposite direction and will properly replicate the feel and response of a right handed knob.
Obviously this is only going to be an issue for you if you like to micro-manage the pots whilst playing, or if you use them for effects such as volume-swells. It's all about having that little bit of extra control over your sound.
It's not something that desperately bothers me personally, but I am
thinking about getting some left handed pots put in my Chapman ML2.
Here's a link to a set of Left Handed EMG Pots
as an example. As you can see it's a cheap problem to rectify
This is a topic I want to do a post on at some point for sure
Did you know that some manufacturers do lefty specific pickups too...