Its just talking about what do these things mean. Organic referring to organic matter so things like leaves, dirt and grass
Inorganic referring to stuff like rocks or pieces of debris that might be stuck on the shoe
Remember that organic things contain carbon (one of the dot points you had to learn about what makes something an organic molecule). and when something has carbon we can do combustion so u can basically figure out how much organic stuff was there through combustion, and the left over will be all the inorganic stuff for the most part