Pollen filter - Which way round? (PIC)

[maxp]

I always assumed a pollen filter / cabin filter should have the arrow pointed in the direction of the air flow. However, I received a genuine ford part for my focus and oddly the arrow seems to point upwards. Can anyone tell me which way round this filter should be fitted?
Also, every video I've seen of them being fitted shows the folded flap bit attached from the top (rather than the bottom with my new one).