GV/SMS

From Docs

When using SMS with Google Voice, there are a couple of things to note.

First is that if you have Google Voice set to deliver SMS messages to your phone, then they will come in the following format:

From: +1 406 NNN NNNN
---------------------
Contact Name: This is a sample text message

Note that area code 406 is fixed; all of the other digits seem to be somewhat random. That phone number is linked from your Google Voice account to that contact's phone number. As far as I can tell, these numbers are permanently fixed, so you could map these to your contacts in your address book.

A better way would be to go into your Google Voice settings and turn off the option to send texts to your phone, and set GV to automatically check your account for new messages. This way, it will notify you when there are new messages. This avoids the confusion of having extra numbers for each contact.