-3.26% is the change from 521 to 504
Calculation steps:
[( 504 - 521 ) ÷ 521] x 100 = -3.26%
Formula
Percentage change = [(504 - 521) / 521] x 100
Subtract the new number by the original number
504 - 521 = -17
-17 ÷ 521 = -0.03262955854126679
-0.03262955854126679 x 100 = -3.26%