The 'extract all lines' option is useful when the column headers (date, description etc.) are obscured by a background so this text is not embedded within the searchable PDF document.
Also, you may edit a template that you created yourself and de-select the checkbox provided at step two of the template creation wizard. This will allow for situations where column headers cannot be found on a bank statement.
The 'extract all lines' option causes StatementReader to assume that a table of transactions exists on every page starting at the top, and ending at the bottom of the page. The occasional additional row may be added because the area processed is larger than the actual table of transactions. Across multiple pages extra lines of data can be quickly identified by sorting the data by the date or amount columns.