-23.84% is the change from 839 to 639
Calculation steps:
[( 639 - 839 ) ÷ 839] x 100 = -23.84%
Formula
Percentage change = [(639 - 839) / 839] x 100
Subtract the new number by the original number
639 - 839 = -200
-200 ÷ 839 = -0.23837902264600716
-0.23837902264600716 x 100 = -23.84%