In browse mode, how many records are in your found set? 3 records perhaps?
In preview mode, fileMaker previews all the records in your found set, not just the current record. If that includes records you do not want to preview, modify your found set to exclude them before entering preview mode.
If you have just one record in your found set there could be issues with your layout design. The total height of all your layout parts ( header + body + sub summar parts + grand summary parts + footer ) may exceed the total height your currently selected printer can print on it's currently selected size of paper.