-21.81% is the change from 321 to 251
Calculation steps:
[( 251 - 321 ) ÷ 321] x 100 = -21.81%
Formula
Percentage change = [(251 - 321) / 321] x 100
Subtract the new number by the original number
251 - 321 = -70
-70 ÷ 321 = -0.21806853582554517
-0.21806853582554517 x 100 = -21.81%