-21.4% is the change from 813 to 639
Calculation steps:
[( 639 - 813 ) ÷ 813] x 100 = -21.4%
Formula
Percentage change = [(639 - 813) / 813] x 100
Subtract the new number by the original number
639 - 813 = -174
-174 ÷ 813 = -0.2140221402214022
-0.2140221402214022 x 100 = -21.4%