-20.93% is the change from 817 to 646
Calculation steps:
[( 646 - 817 ) ÷ 817] x 100 = -20.93%
Formula
Percentage change = [(646 - 817) / 817] x 100
Subtract the new number by the original number
646 - 817 = -171
-171 ÷ 817 = -0.20930232558139536
-0.20930232558139536 x 100 = -20.93%