-84.48% is the change from 638 to 99
Calculation steps:
[( 99 - 638 ) ÷ 638] x 100 = -84.48%
Formula
Percentage change = [(99 - 638) / 638] x 100
Subtract the new number by the original number
99 - 638 = -539
-539 ÷ 638 = -0.8448275862068966
-0.8448275862068966 x 100 = -84.48%