If found a really annoying bug on the current (iOS 9.2) mobile safari (first appearing since iOS 7!)
If you using multi select fields on mobile safari - like this:>
After a long research I found the following (not most beautiful) but working solution:
The trick is to add a empty and disabled select option at the fist position:
This will prevent iOS from automatically selecting the first option and keep the selection values right and clean!
The empty option is not visible and the count of the selections is correct.