-29.74% is the change from 306 to 215
Calculation steps:
[( 215 - 306 ) ÷ 306] x 100 = -29.74%
Formula
Percentage change = [(215 - 306) / 306] x 100
Subtract the new number by the original number
215 - 306 = -91
-91 ÷ 306 = -0.2973856209150327
-0.2973856209150327 x 100 = -29.74%