-20.82% is the change from 807 to 639
Calculation steps:
[( 639 - 807 ) ÷ 807] x 100 = -20.82%
Formula
Percentage change = [(639 - 807) / 807] x 100
Subtract the new number by the original number
639 - 807 = -168
-168 ÷ 807 = -0.20817843866171004
-0.20817843866171004 x 100 = -20.82%