You're cutting off part of his penis and you're worried about too much vitamin K??
I think if you're going to circ you'd better opt for as high a dose of Vit K as you can get -- you're already putting your LO at risk by circumcising; I wouldn't compound the risk by trying to guess at an oral Vit K dosage. In fact, I'd be surprised if any ped would agree to do a circumcision on a baby who has not received a Vit K injection.
I would guess that the oral Vit. K. is intended as a "just in case" supplement for babies who have no complications, bruising, etc. during birth, and is certainly NOT intended for babies who are going under the knife within a few hours of birth.
Please, for the sake of your little one's health and safety -- I would gently encourage you to visit the Case Against Circumcision forum and read some of the resources and links there, and reconsider your decision to circ. It is a medically unnecessary procedure, has all the risks of any elective surgery, and will permanently disfigure your baby. IMO, there is no reason strong enough to argue for it.
you do not have to get the circ done right away. you can wait until the baby is a couple weeks old.
If you are worried about it, I would just wait on the circ until he is producing his own vit K.
While I do certainly recommend thoroughly researching circumcision before following through with it, I would hope that if you've chosen this, it's for a very valid religious or medical reason and you are very confident with your decision to put your newborn through surgery.
That said... my understanding is that the oral doses are not absorbed as well as the shots they give at the hospital, so this is likely the reason for it being a higher dose. I would research this avenue of it, as I think that's likely what you'll find as the reasoning. The hospital shot dose is 20,000 times the normal amount found in a newborn's body... so a 2mg oral dose (if all absorbed...) would bring you up to 40,000 times the body's normal levels.
Also of note-- in another thread here recently, several people point out that the Vit K is most useful for cases of -internal- bleeding and trauma- ie brain bleeds... I don't believe it is very effective for the external trauma and bleeding of circumcision.
Or you could wait on it until he can make his own decisions about his body.
Seriously- unless this is for religious reasons (and even if it is, you can rethink it! http://www.jewsagainstcircumcision.org/) I hope you will do some more research on this. It's not just unnecessary, it's harmful. Someone mentioned the Case Against Circumcision forum. Here's a direct link to it: http://www.mothering.com/community/forum/list/44/the-case-against-circumcision