Additional filter fields in the compendium search function

Hi,

Please can someone explain what I'm doing wrong with the additional filter fields in the compendium search function.

i.e. trying to find all monsters with AC12

I add a new filter, AC, then put 12 in the search bar. All of the monsters in the monster list disappear so I assume it has auto filtered, but nothing else ever comes up?

Thank you for any help you can offer.

Cheers,

S