What's in the last page of your InDesign file?
It's an "About the Author" page, so it just has a heading and 3 paragraphs of standard text. If it matters, there's no images in the epub (aside from the cover, which I set in the export options).
For every object that you have created in InDesign, exporting to epub, a div is generated with id of form idContainerXXX, it is the unique id for that pageitem and the styling attributes applied to it are mapped in corresponding class named as idGenObjectLayout.
This has been a recent change, where we have given a generalised name to all pageitems to keep the HTLM and CSS tidy.
Hope this solves your curiosity..