The folio number is by default the same as the reservations' confirmation number. However, there is a feature in Visual Matrix that gives you the possibility to differentiate those 2 documents' numbers. This is for hotels that have an outside invoicing system or a government requirement that requires sequential receipt numbers. Since folios numbers may not be sequential, this allows to have a sequential number on every single folio that disregards the reservation ID.
Path: Management > Setup > Property > Forms
Use Serial Numbers
While ask for the activation, you will be asked to give the number that will begin the serie. This number will be entered in the "Next Serial #" field.
Append Folio
Appending the folio number adds the reservation ID/Folio number to the serial number, so that you do not entirely hide the number.