Just look at this:
I did the math, 580 = .58 of 1000. I also refreshed the page, clicked on "view vote counts...." I haven't received any rep for a while...
Is it an update issue?
You did the math, but used the wrong base. 0.58 as a binary floating point number is slightly less than the decimal value, since it cannot be represented exactly:
Apparently they always round down the computed result to two decimal digits (i.e. to the next integer percentage), probably to prevent this page from showing an incorrect "100%" when you're at e.g.