Method and apparatus for implementing controlled pre-fetching of data. The counter is comprised of a loader for receiving a cassette, a sensor for sensing whether a cassette is in the loader, means for moving the loader into an operative position, a vacuum unit for applying a vacuum to the cassette, a drive unit for driving a driven portion of the cassette and a counter for counting medication within a portion of the cassette. The length of each of the telescoping rod assemblies is adjustable to accommodate king, queen, double or twin fitted sheets.