Here is the link for the TurboTax audit support center. Even if you didn't purchase Audit Defense, this may help.
I would recommend calling the number on your notice/bill and asking for more information on how they reached that determination. It's a good idea to have the CA return in question printed up or on your computer when you call in case you need to refer to it. Here is the link for the CA Franchise Tax Board MyFTB Account page. It would also be a good idea to check your account activity before you call.
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