-69.04% is the change from 830 to 257
Calculation steps:
[( 257 - 830 ) ÷ 830] x 100 = -69.04%
Formula
Percentage change = [(257 - 830) / 830] x 100
Subtract the new number by the original number
257 - 830 = -573
-573 ÷ 830 = -0.6903614457831325
-0.6903614457831325 x 100 = -69.04%