But "30x" is just another way of saying "3000%". Or, "3000%" is just another way of saying "30x". "Shrinking by 30x" means the same thing as "shrinking by 3000%".
If I had starting capital of 100 usd and it increased by 20x then that means I gained 2000 usd which is 20x of my starting capital.
EDIT: correction 30x is same as 3000%.