The phrase "day supply" refers to the amount of something that will last for one day. It is used to measure how long a certain item or resource will be sufficient for daily use or consumption. Full definition
We will again be conservative, and say that each animal requires only 3 cubic feet living space and three cubic foot for 40 days supply of food. (religion.blogs.cnn.com)
Each bag features a 30 - day supply for a 10 - lb. (petbusiness.com)
We have about a 45 day supply on the market now. (totalmortgage.com)