-25.32% is the change from 857 to 640
Calculation steps:
[( 640 - 857 ) ÷ 857] x 100 = -25.32%
Formula
Percentage change = [(640 - 857) / 857] x 100
Subtract the new number by the original number
640 - 857 = -217
-217 ÷ 857 = -0.2532088681446908
-0.2532088681446908 x 100 = -25.32%