-99.6% is the change from 991 to 4
Calculation steps:
[( 4 - 991 ) ÷ 991] x 100 = -99.6%
Formula
Percentage change = [(4 - 991) / 991] x 100
Subtract the new number by the original number
4 - 991 = -987
-987 ÷ 991 = -0.9959636730575177
-0.9959636730575177 x 100 = -99.6%