Set the starting reading location

[markcrew]

I use calibre to format e-books before loading them on my Kindle in AZW3 format. Books are somehow tagged with a starting reading position, which you can navigate to in many readers. In the calibre Viewer, it's right click -> Go to -> start. On my Kindle reader, it's Go to -> Beginning.

Does anyone know how to set this starting location in a book? When I load a new book into calibre, go through my usual edits (Editing metadata, numbering pages, etc.), and then doing a Convert Books to generate an updated file in AZW3 format, this starting location almost never ends up pointing at the page it should be. How do I update it?

Thanks in advance for the help!

[kovidgoyal]

IIRC its an entry in the guide section in the OPF file of type text