What are the digits on top of the housing for? Steve Giles November 10, 2020 16:54 They are a visual reminder (calendar wheel) to help you remember to change the cartridge every 3 months The numbers represent months and the dots represent weeks When you first install or change the cartridge, rotate the top to reflect 3 months from now This is when you should change the cartridge next Related articles Why does the water comes out as black at first? Can I turn the FloWater Faucet Filter off to wash dishes and use the faucet normally? The FloWater Faucet Filter broke or is leaking after the installation. Is that normal? Can I recycle the FloWater Faucet Filter cartridges? How much does it cost to have the filters in my Refill Station(s) replaced?