66.34% is the change from 306 to 509
Calculation steps:
[( 509 - 306 ) ÷ 306] x 100 = 66.34%
Formula
Percentage change = [(509 - 306) / 306] x 100
Subtract the new number by the original number
509 - 306 = 203
203 ÷ 306 = 0.6633986928104575
0.6633986928104575 x 100 = 66.34%