-29.36% is the change from 906 to 640
Calculation steps:
[( 640 - 906 ) ÷ 906] x 100 = -29.36%
Formula
Percentage change = [(640 - 906) / 906] x 100
Subtract the new number by the original number
640 - 906 = -266
-266 ÷ 906 = -0.293598233995585
-0.293598233995585 x 100 = -29.36%