Qualifying energy use

At p. 455 I read: “Exclude any site-generated electricity (e.g. wind turbines, photovoltaics) and fuel (e.g., biogas) from the total consumption amount, provided the project does not sell the on-site energy generated as RECs”. I have some doubts. 1. Shall one exclude only the renewable energy? In equation 1 (p. 456) the word “renewable” is used for fuels but it isn’t for electricity. Does it mean that electricity and fuels are considered in different ways? 2. In equation 1 I read “total annual grid-based electricity use”. Does it mean energy that is bought from the grid? In that equation the “Total annual site-generated electricity” is then subtracted from the “total annual grid-based electricity use”. If the “total annual grid-based electricity use” refers only to electricity that is bought from the grid, it seems that the result of that subtraction can be even negative. In fact, consider a building where more than 50% of the used electricity is site-generated.