-95.15% is the change from 639 to 31
Calculation steps:
[( 31 - 639 ) ÷ 639] x 100 = -95.15%
Formula
Percentage change = [(31 - 639) / 639] x 100
Subtract the new number by the original number
31 - 639 = -608
-608 ÷ 639 = -0.9514866979655712
-0.9514866979655712 x 100 = -95.15%