-32.63% is the change from 950 to 640
Calculation steps:
[( 640 - 950 ) ÷ 950] x 100 = -32.63%
Formula
Percentage change = [(640 - 950) / 950] x 100
Subtract the new number by the original number
640 - 950 = -310
-310 ÷ 950 = -0.3263157894736842
-0.3263157894736842 x 100 = -32.63%