-68.7% is the change from 821 to 257
Calculation steps:
[( 257 - 821 ) ÷ 821] x 100 = -68.7%
Formula
Percentage change = [(257 - 821) / 821] x 100
Subtract the new number by the original number
257 - 821 = -564
-564 ÷ 821 = -0.6869671132764921
-0.6869671132764921 x 100 = -68.7%