-97.5% is the change from 521 to 13
Calculation steps:
[( 13 - 521 ) ÷ 521] x 100 = -97.5%
Formula
Percentage change = [(13 - 521) / 521] x 100
Subtract the new number by the original number
13 - 521 = -508
-508 ÷ 521 = -0.9750479846449136
-0.9750479846449136 x 100 = -97.5%