If you've imported and are working with a particularly large dataset, you may see message when you scroll to the bottom of the sheet indicating "... and X more rows. Search or filter to reduce the size of your dataset."
HTML has a limit on the height of a table, limiting the number of rows we can show at once in a table in Flatfile's Platform. If this limit is reached by your file or dataset, the table can still be filtered or searched through to make sure you can access all records.