Emailing John to clarify your specs is the best idea, but re sending a sample......
Now that you're going 'custom' and fine tuning your system, its a good idea to take samples from as many areas as possible and label them accordingly.
Hair naturally is different colours in different areas and a good factory will mix and blend to reproduce that.
If you can only send one sample, then it should be from as near to your face as possible as this tends to be where hair is lightest. The factory will then take that into account and vary the colour accordingly.

Good Luck!