-66.27% is the change from 830 to 280
Calculation steps:
[( 280 - 830 ) ÷ 830] x 100 = -66.27%
Formula
Percentage change = [(280 - 830) / 830] x 100
Subtract the new number by the original number
280 - 830 = -550
-550 ÷ 830 = -0.6626506024096386
-0.6626506024096386 x 100 = -66.27%