Nope you got it right..all I can say is the math works. A 2+5 offset is the right numbers needed to centre the rim as perfectly as can be attained in this application..
I think my math had it to within 1/4" when I 1st did it and it came up good for me.
In mass produced parts there are acceptable tolerances..my guess is the ones you got weren't as close on the true math as some.
But it isn't of great concern..as long as there is decent clearance to the forks, the slight side to side shift of the offset won't be perceptible to the ride..
And it looks pretty sick just the same!!
Current toys..
1986 Honda 350X..trail bomb!
1985 Honda 250SX..my main mudder
1985 Honda 250ES..Back in Black Trike
Current non-trike toys:
1990 Honda TRX300FW
1995 Seadoo GTX
1998 Polaris Indy Lite 340(Nearly new looking)
1998 Polaris Touring 500
1998 Club Car (electric)