-1.08% is the change from 830 to 821
Calculation steps:
[( 821 - 830 ) ÷ 830] x 100 = -1.08%
Formula
Percentage change = [(821 - 830) / 830] x 100
Subtract the new number by the original number
821 - 830 = -9
-9 ÷ 830 = -0.010843373493975903
-0.010843373493975903 x 100 = -1.08%