Original: It is probably the fifth most massive asteroid after Ceres, Vesta, Pallas, and Hygiea, with a mass estimated to be 1.2% of the mass of the entire asteroid belt.
Simplified: It is the fifth heaviest asteroid after Ceres, Vesta, Pallas and Hygiea, and scientists think that it makes up 2.0% of the mass of the whole asteroid belt.