-20.66% is the change from 639 to 507
Calculation steps:
[( 507 - 639 ) ÷ 639] x 100 = -20.66%
Formula
Percentage change = [(507 - 639) / 639] x 100
Subtract the new number by the original number
507 - 639 = -132
-132 ÷ 639 = -0.20657276995305165
-0.20657276995305165 x 100 = -20.66%