New Oven Confusion

I've bought a new oven. It's gas, and we use bottled. I've changed the burners, as it came with town gas burners installed.

But the instruction book then tells me to adjust the minimum gas level, and there's a different method depending on whether:

a) Passage du gaz naturel au gaz liquifié
or
b) Passage du gaz liquifiée au gaz naturel

I know what all those words mean individually, but I don't have a clue what they mean in this context. How can I possibly be converting natural gas into liquified gas?

Can anyone clarify?

No. It's referring to setting the minimum gas level by way of an adjustment screw next to the control knob.

Thank you. It made no bloody sense to me, but now it does.