-61.56% is the change from 640 to 246
Calculation steps:
[( 246 - 640 ) ÷ 640] x 100 = -61.56%
Formula
Percentage change = [(246 - 640) / 640] x 100
Subtract the new number by the original number
246 - 640 = -394
-394 ÷ 640 = -0.615625
-0.615625 x 100 = -61.56%