I am going to try to clean this filter for the first time. please let me know how much DE I am meant to add back in. I think it is 6 pounds but just want to make sure. I am confused because as I understand it, it is about a pound per 10 ft.². I believe this is 60 ft.². however, on this little chart that is on the filter label, it shows the FNS 60 being 150 ft.². don’t understand.