-34.49% is the change from 977 to 640
Calculation steps:
[( 640 - 977 ) ÷ 977] x 100 = -34.49%
Formula
Percentage change = [(640 - 977) / 977] x 100
Subtract the new number by the original number
640 - 977 = -337
-337 ÷ 977 = -0.34493346980552714
-0.34493346980552714 x 100 = -34.49%