-39.05% is the change from 507 to 309
Calculation steps:
[( 309 - 507 ) ÷ 507] x 100 = -39.05%
Formula
Percentage change = [(309 - 507) / 507] x 100
Subtract the new number by the original number
309 - 507 = -198
-198 ÷ 507 = -0.3905325443786982
-0.3905325443786982 x 100 = -39.05%