The real size of your page contents may differ from the desired visible size. This can happen when page contents extend beyond the page boundaries (including masked contents) or when the contents are smaller than the page stage size.
To resolve this issue, specify the desired page size in the page list. For example, your page should be 300x500 pixels in size, but it is scaling incorrectly. In this case, declare this page as follows in the file js/bookSettings.js:
flippingBook.pages = [ "pages/page-001.swf", "pages/page-002.swf?w=300%26h=500", "pages/page-003.swf", "pages/page-004.swf" ]