My understanding is that the blend number doesn't mean much by itself but is a revolving, continuous number that is the actual build sequence. So in coonjunction with the build date it gives you the sequence.
So j051499, Blubyu & I have build dates of 5/14. My blend is 7227, j051499 is 7499 and I think Blubyu's was higher. You will also notice that westhuron has a build date of 5/17 and blend of 8103. That seems to bear that out and somewhere between Blubyu and westhuron's blend #'s is the break between Friday and Monday. (I am assuming they aren't building Saturday & Sunday.)
Edit: Just checked Blubyu is blend 7287, so it should be mine, Blubyu and j051499 with other lucky buyers in between.
2011 GT Prem 401A Convertible - Sterling Grey, Red Interior, Manual, Elect/Comfort/HID/Sec