-99.8% is the change from 506 to 1
Calculation steps:
[( 1 - 506 ) ÷ 506] x 100 = -99.8%
Formula
Percentage change = [(1 - 506) / 506] x 100
Subtract the new number by the original number
1 - 506 = -505
-505 ÷ 506 = -0.9980237154150198
-0.9980237154150198 x 100 = -99.8%