-90.09% is the change from 646 to 64
Calculation steps:
[( 64 - 646 ) ÷ 646] x 100 = -90.09%
Formula
Percentage change = [(64 - 646) / 646] x 100
Subtract the new number by the original number
64 - 646 = -582
-582 ÷ 646 = -0.9009287925696594
-0.9009287925696594 x 100 = -90.09%