Weird 'pre' numbering and addition to ToC. [Help]

Hi,

Sorry to ask, but couldn’t find the answer to my problem. When I compile my book, they look perfectly fine on iOS and in the Kindle Previewer app. However, every Android-based reader app I tried, gives me weird results. Especially when it comes to ToC.

First of all, it starts numbering my ToC elements (See attached pic.)
Then, it puts some weird addition to the Toc, called ‘Guide’ with two links to ‘Contents’ and ‘Start of Content’
Does anyone know how to fix this?

Thanks very much.