codes on the backs of film prints

Does anyone know how to interpret the codes on the backs of minilab prints?
I remember seeing some info about this somewhere - not sure whether on this site or elsewhere.

Thanks,
Yaron

First, there are some threads related to this on www.photo.net. Search for "codes" or somesuch. But those threads are a little inconclusive.

I called the two labs that I'm trying out right now. The two have different codes (presumably b/c they use different machine).

One lab has codes such as: +00+00+00-02 000000
The four signed numbers refer to cyan, yellow, magenta, and density correction.
(Density can be thought of as darkness/lightness. Negative number = less density = lighter picture.)
One number shift corresponds to half a stop.
The final '000000', I was told, is meaningless.

The other lab has codes such as: N N N N-2 NN
The first four values again corresponds to cyan, yellow, magenta, and density correction.
As for the final NN, that's some automatic correction that the computer does on printing. The person told me he has no control over this, but it's barely ever perceptible.

- Yaron