-96.4% is the change from 639 to 23
Calculation steps:
[( 23 - 639 ) ÷ 639] x 100 = -96.4%
Formula
Percentage change = [(23 - 639) / 639] x 100
Subtract the new number by the original number
23 - 639 = -616
-616 ÷ 639 = -0.9640062597809077
-0.9640062597809077 x 100 = -96.4%