-38.78% is the change from 820 to 502
Calculation steps:
[( 502 - 820 ) ÷ 820] x 100 = -38.78%
Formula
Percentage change = [(502 - 820) / 820] x 100
Subtract the new number by the original number
502 - 820 = -318
-318 ÷ 820 = -0.3878048780487805
-0.3878048780487805 x 100 = -38.78%