So, after more digging and a few experiments with the rental property session, I found a workaround of this issue:
When putting the information of the rental property, only put the days for rental and leave the personal usage day as ZERO, then manually modify the federal deduction part for property tax and mortgage interest by multiplying the "primary home days / total days of the year" ratio, and put the "rental days/total days of the year" part into the rental property expense session.
It turned out that the "personal usage" days in the rental property session will automatically calculate the federal deduction part for property tax and mortgage interest, but it will use the same ratio on the entire rental property expenses and depreciation later, which is buggy.
To get the expense and depreciation correct, especially for the first year converted to rental property, just input the exact rental usage days and leave the personal usage day as zero, in this way, you will have to split the mortgage interest and property tax into two parts, and fill them separately into the rental property session as well as the federal deduction (Schedule A), but at least you will get the expense and depreciation correct for the long term.
