-4.88% is the change from 820 to 780
Calculation steps:
[( 780 - 820 ) ÷ 820] x 100 = -4.88%
Formula
Percentage change = [(780 - 820) / 820] x 100
Subtract the new number by the original number
780 - 820 = -40
-40 ÷ 820 = -0.04878048780487805
-0.04878048780487805 x 100 = -4.88%