What is the fuelling floor?

It is the daily energy that covers the training you are currently doing, stated as a figure with nothing attached to it. It is a floor, not a target and not a cap: it says what your training is asking for, and it does not tell you to eat a particular amount. If too few days of food are logged to work it out, it says so instead of showing a number. The constants behind it are published on Settings > Help > How it works.