63.75% is the change from 309 to 506
Calculation steps:
[( 506 - 309 ) ÷ 309] x 100 = 63.75%
Formula
Percentage change = [(506 - 309) / 309] x 100
Subtract the new number by the original number
506 - 309 = 197
197 ÷ 309 = 0.6375404530744336
0.6375404530744336 x 100 = 63.75%