-15.49% is the change from 639 to 540
Calculation steps:
[( 540 - 639 ) ÷ 639] x 100 = -15.49%
Formula
Percentage change = [(540 - 639) / 639] x 100
Subtract the new number by the original number
540 - 639 = -99
-99 ÷ 639 = -0.15492957746478872
-0.15492957746478872 x 100 = -15.49%