[Koha] Problem with Label Creator

I find a difficluty with printing long lines in the Biblio Label Creator. Actually, it depends on the way in which a layout for labels is created. When I create the layout and I select the order of fields to be printed from drop-down menus, everything is OK. But when I create a layout, listing the fields to be printed (like "245a, 952o" ecc.), each line is cut after a few words. Would anyone know how to fix this problem? I'm using Koha 3.00001. Thank you Ondrej Mlecka