Simplify the following text for a Grade 5 native English-speaking person.
Original: The total mass of the erupted material ( including magma ) was 35 million tonnesâ '' only 3 % of the amount that erupted from Mount St. Helens in 1980 .
Simplified: The amount of magma erupted from the volcano was 3 % of that from Mount St. Helens in 1980 .