FFA

Free Fatty Acids or FFAs are a breakdown product from triglycerides. The levels give an indication of oil quality based on fruit quality and handling. Lower is better and oils with lower levels will tend to have longer shelf lives. The number indicates the percentage of grams of FFAs relative to the grams of Oleic acid in 100gms of oil. To qualify as extra-virgin, an oil has to have a FFA level lower than 0.8%. Virgin olive oil has an FFA level between 0.8 and 2%. Oils with levels above 2% aren't considered food quality. The non-edible oil is called lampante in the EU because that was the kind of oil you would traditionally burn in a lamp.

References:

Olive oil acidity

What the Olive Oil Quality Tests Tell Us