-75% is the change from 512 to 128
Calculation steps:
[( 128 - 512 ) ÷ 512] x 100 = -75%
Formula
Percentage change = [(128 - 512) / 512] x 100
Subtract the new number by the original number
128 - 512 = -384
-384 ÷ 512 = -0.75
-0.75 x 100 = -75%
Example