-99.69% is the change from 639 to 2
Calculation steps:
[( 2 - 639 ) ÷ 639] x 100 = -99.69%
Formula
Percentage change = [(2 - 639) / 639] x 100
Subtract the new number by the original number
2 - 639 = -637
-637 ÷ 639 = -0.9968701095461658
-0.9968701095461658 x 100 = -99.69%