Hi neelhound.
As others have explained, the 2nd gauge is measuring Bar.
To assist in your understanding, PSI (pounds per square inch), is not loads more than Bar as you suspected. The general rule of thumb is that there are 14.5 PSI to 1 Bar, give or take a few decimal places.
I don't mean to sound condescending in any way, I'm just trying to pass on knowledge that I've gained during my working life using compressed gases and air.
On a cautionary note, a quick glance at the calculator will tell you that a CO2 bottle filled to 60 Bar equates to approx. 870 psi. Seriously, enough to take your head off. I've seen a few 'mishaps' with compressed gases and air over the years and they are not a pretty sight.
To put this into perspective, you may have heard the almighty bang when a car tyre explodes, well that's only filled to around 2 to 2.2 Bar. Imagine that bang amplified 30 times. Stand well clear and get the ear plugs out.
Another word of advice I can offer is that if you get your CO2 cylinders refilled, don't let them rattle around in the boot of your car and transport them with the horn fitted.
If one was to accidentally discharge in the boot of your car without without the horn fitted, you would have a jet of CO2 at 870 psi which is enough to blow your boot lid off.
and at the same time turn your cylinder into a rocket. With the horn fitted, the gas first encounters a right angled bend which reduces the pressure some and then it is reduced even further by being 'spread' over a wider area via the horn.
Sorry, I seem to have gone off on one here but all I can say is treat your CO2 cylinders with respect and you should have no problems.
Hope this clarified your original query anyway. As I was once told at college, "It's easy if you understand it, if you don't understand it, it's impossible". This statement can be applied to anything in life, it's a bit like this planted tank game really.
Chris.