-17.97% is the change from 512 to 420
Calculation steps:
[( 420 - 512 ) ÷ 512] x 100 = -17.97%
Formula
Percentage change = [(420 - 512) / 512] x 100
Subtract the new number by the original number
420 - 512 = -92
-92 ÷ 512 = -0.1796875
-0.1796875 x 100 = -17.97%