Agreed with the state tax holding is box 17 of W-2. The additional tax withholding come from an entry that can be done in Turbotax for "payment when filing tax extension". It has been used in Turbotax for calcualting the tax withholding. Once the entry is set, it won't change anymore. Therefore the tax withholding the box 17 + the initial entry for "payment when filing tax extension" and cannot be modified even the "payment when filing tax extension" was modified.
