Because that's not how the math works in the actual way delegates are determined. It is broken up in a way that breaks toward Hillary. It's also simplified because WY only has one congressional district.
(the percentage is separately run against At Large, CD, and bound PLEO delegate totals, then added up)
There are 8 CD delegates, 55.7% for B gives him 4.457 Delegates to 3.543. Rounded to 4-4
There are 4 At-Large delegates, 55.7% for B gives him 2.23 to 1.77. Rounded to 2-2.
There are 2 Bound PLEO delegates, 55.7% for B gives him 1.12 to 0.88. Rounded to 1-1.
http://www.thegreenpapers.com/P16/WY-D