-21.07% is the change from 840 to 663
Calculation steps:
[( 663 - 840 ) ÷ 840] x 100 = -21.07%
Formula
Percentage change = [(663 - 840) / 840] x 100
Subtract the new number by the original number
663 - 840 = -177
-177 ÷ 840 = -0.21071428571428572
-0.21071428571428572 x 100 = -21.07%