Issue with filter selection

The filter by special features section doesn’t quite work as we wanted. What was want is for the filter to be additive- so if the customer selects automatic magnification reading, extended depth of field and polarising, then they should just see the DinoLites that have these three features.

At present, if you click on the automatic magnification reading, you see the 15 DinoLites that have this feature. But if you then also click on the polariser feature you then see 25 DinoLites that have automatic magnification reading or polariser. What it should show is those that have automatic magnification reading and polariser.

The page I need help with: [log in to see the link]