-21.08% is the change from 816 to 644
Calculation steps:
[( 644 - 816 ) ÷ 816] x 100 = -21.08%
Formula
Percentage change = [(644 - 816) / 816] x 100
Subtract the new number by the original number
644 - 816 = -172
-172 ÷ 816 = -0.2107843137254902
-0.2107843137254902 x 100 = -21.08%