-87.01% is the change from 639 to 83
Calculation steps:
[( 83 - 639 ) ÷ 639] x 100 = -87.01%
Formula
Percentage change = [(83 - 639) / 639] x 100
Subtract the new number by the original number
83 - 639 = -556
-556 ÷ 639 = -0.8701095461658842
-0.8701095461658842 x 100 = -87.01%