-89.9% is the change from 505 to 51
Calculation steps:
[( 51 - 505 ) ÷ 505] x 100 = -89.9%
Formula
Percentage change = [(51 - 505) / 505] x 100
Subtract the new number by the original number
51 - 505 = -454
-454 ÷ 505 = -0.899009900990099
-0.899009900990099 x 100 = -89.9%