-61.33% is the change from 830 to 321
Calculation steps:
[( 321 - 830 ) ÷ 830] x 100 = -61.33%
Formula
Percentage change = [(321 - 830) / 830] x 100
Subtract the new number by the original number
321 - 830 = -509
-509 ÷ 830 = -0.6132530120481928
-0.6132530120481928 x 100 = -61.33%