"Buttons and forms" isn't working

That's not a button, it's a combo box. I'm not sure why you would expect that 11 to be there when it's not part of the list.

Regarding PDF interactive buttons, you can have a word or words or an image (such as a button shape) as a document hyperlink to say another page in the document, or to an external website. Some devices, for example, iPads, don't have rollover capability – only click – you should avoid multi-action buttons like On Click, On Roll Over, etc.  Multi-state objects (MSO) don’t work at all in Interactive PDFs. 

As an alternative to Interactive PDF, consider using InDesign's Publish Online feature instead – this format, which is HTML5, can be viewed on any device with a compatible browser – PC, Mac, Tablet or Smart Phone and will support all kinds of interactive features and more.

PDF interactivity can be unpredictable. The many available viewers will produce varied results, and unfortunately, you should expect to encounter aspects of it that simply won't work the way you intend.

In this case, I'd ask whether the "button" is a separate object from the text frame containing the number. Upon export all interactive elements come to the front, and anything they were stacked behind may get covered up.

Which format are you exporting to?