-37.68% is the change from 820 to 511
Calculation steps:
[( 511 - 820 ) ÷ 820] x 100 = -37.68%
Formula
Percentage change = [(511 - 820) / 820] x 100
Subtract the new number by the original number
511 - 820 = -309
-309 ÷ 820 = -0.37682926829268293
-0.37682926829268293 x 100 = -37.68%