-21.38% is the change from 814 to 640
Calculation steps:
[( 640 - 814 ) ÷ 814] x 100 = -21.38%
Formula
Percentage change = [(640 - 814) / 814] x 100
Subtract the new number by the original number
640 - 814 = -174
-174 ÷ 814 = -0.21375921375921375
-0.21375921375921375 x 100 = -21.38%