-21.33% is the change from 647 to 509
Calculation steps:
[( 509 - 647 ) ÷ 647] x 100 = -21.33%
Formula
Percentage change = [(509 - 647) / 647] x 100
Subtract the new number by the original number
509 - 647 = -138
-138 ÷ 647 = -0.2132921174652241
-0.2132921174652241 x 100 = -21.33%