From Utilities | App Designer | Import/Export, an app is created to export a data set from a table to Excel, txt, etc. Opening the exported data file shows the incorrect number of rows.
Could be caused by a connection to the wrong database.
Open up the app you created and check the bottom left corner to make sure the connection is to the proper database. If not you can change the connection info by clicking the 'Change session for action' icon on the top left.