-90.45% is the change from 639 to 61
Calculation steps:
[( 61 - 639 ) ÷ 639] x 100 = -90.45%
Formula
Percentage change = [(61 - 639) / 639] x 100
Subtract the new number by the original number
61 - 639 = -578
-578 ÷ 639 = -0.9045383411580594
-0.9045383411580594 x 100 = -90.45%