-39.16% is the change from 830 to 505
Calculation steps:
[( 505 - 830 ) ÷ 830] x 100 = -39.16%
Formula
Percentage change = [(505 - 830) / 830] x 100
Subtract the new number by the original number
505 - 830 = -325
-325 ÷ 830 = -0.39156626506024095
-0.39156626506024095 x 100 = -39.16%