-26.21% is the change from 866 to 639
Calculation steps:
[( 639 - 866 ) ÷ 866] x 100 = -26.21%
Formula
Percentage change = [(639 - 866) / 866] x 100
Subtract the new number by the original number
639 - 866 = -227
-227 ÷ 866 = -0.26212471131639725
-0.26212471131639725 x 100 = -26.21%