-2.8% is the change from 642 to 624
Calculation steps:
[( 624 - 642 ) ÷ 642] x 100 = -2.8%
Formula
Percentage change = [(624 - 642) / 642] x 100
Subtract the new number by the original number
624 - 642 = -18
-18 ÷ 642 = -0.028037383177570093
-0.028037383177570093 x 100 = -2.8%