-80.55% is the change from 509 to 99
Calculation steps:
[( 99 - 509 ) ÷ 509] x 100 = -80.55%
Formula
Percentage change = [(99 - 509) / 509] x 100
Subtract the new number by the original number
99 - 509 = -410
-410 ÷ 509 = -0.8055009823182712
-0.8055009823182712 x 100 = -80.55%