-30.36% is the change from 919 to 640
Calculation steps:
[( 640 - 919 ) ÷ 919] x 100 = -30.36%
Formula
Percentage change = [(640 - 919) / 919] x 100
Subtract the new number by the original number
640 - 919 = -279
-279 ÷ 919 = -0.30359085963003263
-0.30359085963003263 x 100 = -30.36%