Yes, the entire volume of air in the room should pass through the filter 4 times an hour for allergy control.
I did some digging and the 380 will only do a little more than one air change per hour in the max rated room size (roughly 25x25 with 9' ceilings). It is only going to provide adequate allergen control in a bedroom sized area. It's, unfortunately, a rather low powered air purifier when you look past all the bells and whistles. I looked into purchasing the same model. If you have it in a big room, it's probably doing little to nothing for the allergy situation.