-33.37% is the change from 959 to 639
Calculation steps:
[( 639 - 959 ) ÷ 959] x 100 = -33.37%
Formula
Percentage change = [(639 - 959) / 959] x 100
Subtract the new number by the original number
639 - 959 = -320
-320 ÷ 959 = -0.33368091762252344
-0.33368091762252344 x 100 = -33.37%