It means that it increases like compound interest.
If you have a building that houses 1000 trimps, and you boost it 5 times at 10% each time it will increase to 1100, 1210, 1331, 1464, 1610.
There is also additive, which is like simple interest. If you have a base of 1000, and boost it 5 times at 10%, then it will increase 1100, 1200, 1300, 1400, 1500.
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