I did did not look to see how California does it
Edit: I just looked at the examples on the California website and I am guessing that California does book number and ticket number
while leaving off the game number. So yyyyyyyy-zzzz my guess is "y" is the book number and "z" is the ticket number.
Otherwise if you are familiar with the way California does the numbering and you know you are correct then your retailer may have a pack of earlier tickets that have not been selling or that were sitting in a warehouse for awhile before being sent to the retailer you bought them at.
Or if my guess is correct...{yyyyyyyy-zzzz}
If there are 30 tix per book then 1182345 * 30 = 35,470,350 tickets. Now if you really do have book #1182345 and there are only 18,000,000 tickets then California, like most states, skips book numbers as a security measure.
There was a story here on lottery post several years ago about a woman in Texas who kept winning on scratchers because she figured out the numbering system. I do not know if that is when the lotteries started skipping book numbers or if they have always skipped them.
Here, in Michigan, I always figure out how many books there should be and I multiply by a fudge factor to take a guess at what the book number ranges the prize might be in but I have never won anything big.
There was also a story about a guy in Canada who figured out which tickets were winners and told the Canadian lottery jurisdiction he was in and they ignored him. He then went out and bought...I think it was around 30 tickets...didn't scratch them and mailed them to the lottery with a letter. When the lottery looked into it something like 28 out of the 30 were unscratched winners so they changed their ticket printing system after that.
Since you are in California and probably know how they do things the odds are you got tickets from an earlier book.
Good Luck!