-99.37% is the change from 639 to 4
Calculation steps:
[( 4 - 639 ) ÷ 639] x 100 = -99.37%
Formula
Percentage change = [(4 - 639) / 639] x 100
Subtract the new number by the original number
4 - 639 = -635
-635 ÷ 639 = -0.9937402190923318
-0.9937402190923318 x 100 = -99.37%