When a report spans multiple pages and is exported to Excel it will be exported to one worksheet. When you then add this same report to a bundle and export to excel it will be exported as multiple worksheets (one per page). This occurs because the columns in a bundle of reports are not continuous (like an excel worksheet) and therefore page breaks are used to create separate worksheets.
Ideally you may prefer that these breaks occur only after each report. In this video we show you how to remove the page breaks from reports and therefore export reports from a bundle to a single worksheet in Excel. Please note since this solution uses a continuous page you may introduce printing issues.