-22.71% is the change from 828 to 640
Calculation steps:
[( 640 - 828 ) ÷ 828] x 100 = -22.71%
Formula
Percentage change = [(640 - 828) / 828] x 100
Subtract the new number by the original number
640 - 828 = -188
-188 ÷ 828 = -0.22705314009661837
-0.22705314009661837 x 100 = -22.71%