-20.72% is the change from 806 to 639
Calculation steps:
[( 639 - 806 ) ÷ 806] x 100 = -20.72%
Formula
Percentage change = [(639 - 806) / 806] x 100
Subtract the new number by the original number
639 - 806 = -167
-167 ÷ 806 = -0.20719602977667495
-0.20719602977667495 x 100 = -20.72%