-96.43% is the change from 840 to 30
Calculation steps:
[( 30 - 840 ) ÷ 840] x 100 = -96.43%
Formula
Percentage change = [(30 - 840) / 840] x 100
Subtract the new number by the original number
30 - 840 = -810
-810 ÷ 840 = -0.9642857142857143
-0.9642857142857143 x 100 = -96.43%