I gave the supplier a call.
They told me, you cut it to length and stick it on top of the cutting strip.
It then acts as the carrier sheet for whatever you are cutting that doesn't have the carrier sheet, in this case paper or thin card.
It is supposed to protect the cutting strip from damage.
It is sold by length, by the metre here, and you only need to put it down in the area you will be cutting.
So, if you are going to be cutting A4 sheets of paper, you only need to put down a piece long enough to cover the length of the side of the paper sheet.
When it wears out, replace it with a new piece.
When you go back to cutting vinyl, remove it all together.
I have ordered a metre, out of curiosity, to see how it goes.