Id go with dachopper advice.
Sometimes have to ignore the top & bottom end of kite cos rated wind charts but comparing the centre points should put you in the ball park.
@Paul 1 - a bit harsh there dude. What eppo said is a pretty valuable bit of an explaination (imo)
I cant see anything wrong with kite cos labelling kites according to wind range for an average kiter. If they could do that accurately it would be a great reference scale for buyers to be guided by. Problem is though that it becomes an arbitary decision based on the impression of those who do the labelling so you are bound to get differing interpretations.
Remember we are still in our infancy in this sport. Im sure over time all the grey areas will become defined areas. Like the concensus among kite cos to go with 'same length' & 'kook proof lines'. And more recently with the 'push away' QR at the head of the chicken loop. These were far more important issues than having an 'exact' indication of kite performance by no.
All in the fullness of time !!!