Let me give you some more info that might also be helpful.
The way that the DVs are kept at those numbers or higher is through a binary OR operation with either 8 or 9. This means that def, spd, and spc can only have a binary value of the form 1xxx. And atk has to fit the form of 1xx1.
Now for a little math. There are 4 possible values for atk and 8 possible values for the other three. Multiply it all together and you get a total of 2048 possible DV combinations for gift Pokemon.
Shiny Pokemon must have the 2nd bit of the atk DV be a 1, and the other DV values must all be 10 exactly. This means the only atk DV values allowed for a shiny gift pokemon are eleven (1011) and fifteen (1111)
This gives the overall shiny chance for a gift pokemon to be 1 in 1024 instead of the standard 1 in 8192.