70.26% is the change from 306 to 521
Calculation steps:
[( 521 - 306 ) ÷ 306] x 100 = 70.26%
Formula
Percentage change = [(521 - 306) / 306] x 100
Subtract the new number by the original number
521 - 306 = 215
215 ÷ 306 = 0.7026143790849673
0.7026143790849673 x 100 = 70.26%