If feeding is perfectly straight, you will need 54 meters of leading loss like blue lines of media path diagram as below.

However, normally it will take some more meters to be stabilized in straight feeding, so please consider 10 meters loss at starting safely.

When you change a roll at unwinder, you can cut and connect the edges and minimize the loss. In this case, there’ll be no loss ideally, but please consider 3~4 meters loss for stabilization of new roll’s straight feeding.