-50.78% is the change from 510 to 251
Calculation steps:
[( 251 - 510 ) ÷ 510] x 100 = -50.78%
Formula
Percentage change = [(251 - 510) / 510] x 100
Subtract the new number by the original number
251 - 510 = -259
-259 ÷ 510 = -0.5078431372549019
-0.5078431372549019 x 100 = -50.78%