-2.53% is the change from 830 to 809
Calculation steps:
[( 809 - 830 ) ÷ 830] x 100 = -2.53%
Formula
Percentage change = [(809 - 830) / 830] x 100
Subtract the new number by the original number
809 - 830 = -21
-21 ÷ 830 = -0.02530120481927711
-0.02530120481927711 x 100 = -2.53%