-90.29% is the change from 309 to 30
Calculation steps:
[( 30 - 309 ) ÷ 309] x 100 = -90.29%
Formula
Percentage change = [(30 - 309) / 309] x 100
Subtract the new number by the original number
30 - 309 = -279
-279 ÷ 309 = -0.9029126213592233
-0.9029126213592233 x 100 = -90.29%