A4r is A4 turned 90 degrees. Stands for A4 reduction. This size is set on the cassette.
On the cassette draw there will be an adjuster to set the size of paper in the tray. Old machine now and I cant remember just where it is but is customer usable so should be easy to find. Also a good idea to take out the paper tray and look behind it to see if paper has gone over the back and upset the sensors.
Bob, February 2008
Quite often the paper size is set by a magnet assy in the paper tray this could have moved or missing altogether. The location of the mag assy is to be found on the tray that goes into the copier
