-34.15% is the change from 820 to 540
Calculation steps:
[( 540 - 820 ) ÷ 820] x 100 = -34.15%
Formula
Percentage change = [(540 - 820) / 820] x 100
Subtract the new number by the original number
540 - 820 = -280
-280 ÷ 820 = -0.34146341463414637
-0.34146341463414637 x 100 = -34.15%