Do you have a W-2 that lists the same state twice in Box 15, so CA in Box 15 and an amount in Box 16 and then ANOTHER line with CA in box 15 and another amount in box 16?
If yes, only enter CA in Box 15 ONCE and then add the total of the two box 16 amounts and enter that total in Box 16 on the same line.
In other words, condense the two entries into one line.
If you're dealing with something different, please continue your question.