-21.8% is the change from 399 to 312
Calculation steps:
[( 312 - 399 ) ÷ 399] x 100 = -21.8%
Formula
Percentage change = [(312 - 399) / 399] x 100
Subtract the new number by the original number
312 - 399 = -87
-87 ÷ 399 = -0.21804511278195488
-0.21804511278195488 x 100 = -21.8%