-98.5% is the change from 999 to 15
Calculation steps:
[( 15 - 999 ) ÷ 999] x 100 = -98.5%
Formula
Percentage change = [(15 - 999) / 999] x 100
Subtract the new number by the original number
15 - 999 = -984
-984 ÷ 999 = -0.984984984984985
-0.984984984984985 x 100 = -98.5%