Ditto is an extension to the standard windows clipboard. It saves each item placed on the clipboard allowing you access to any of those items at a later time.
So Ditto in RICC can be very useful that you can copy all the NODEB and RNC printouts in advance and then paste it later in WCin. For Example you can configure the short-cuts crtl-1, crlt-2 upto 0 in order to paste later the printout selections.