-9.88% is the change from 921 to 830
Calculation steps:
[( 830 - 921 ) ÷ 921] x 100 = -9.88%
Formula
Percentage change = [(830 - 921) / 921] x 100
Subtract the new number by the original number
830 - 921 = -91
-91 ÷ 921 = -0.0988056460369164
-0.0988056460369164 x 100 = -9.88%