It's pretty much linear, so 13,000kPa (130 bar) it has about 1/2 the amount of gas in the cylinder still compared to for instance 26,000kPa (260 bar)
I don't know what the normal 'full fill' cylinder pressure in Australia is, but here in Europe it's usually either 20,000kPa (200 bar) for most cylinders with a push towards newer 30,000kPa (300 bar) ones.
Move to extra high pressure cylinders is to get additional gas in the same cylinder size or to be able to use a smaller size cylinder (eg. for portability) ans still get the same stored volume as a bigger 200 bar one. (of course needs specific new cylinders and regulators)
Still, a good regulator should be able to work over the whole range and close to it's final outlet pressure while maintaining a steady flow rate so these markings on your gauge are not that interesting. Can be a quick visual indicator it you have many bottles though.
Bye, Arno.