-30.96% is the change from 927 to 640
Calculation steps:
[( 640 - 927 ) ÷ 927] x 100 = -30.96%
Formula
Percentage change = [(640 - 927) / 927] x 100
Subtract the new number by the original number
640 - 927 = -287
-287 ÷ 927 = -0.30960086299892126
-0.30960086299892126 x 100 = -30.96%