-21.05% is the change from 817 to 645
Calculation steps:
[( 645 - 817 ) ÷ 817] x 100 = -21.05%
Formula
Percentage change = [(645 - 817) / 817] x 100
Subtract the new number by the original number
645 - 817 = -172
-172 ÷ 817 = -0.21052631578947367
-0.21052631578947367 x 100 = -21.05%