I didn't intentionally mess with the Fair Rental Days field - I'm certain there was some prompt within the online TurboTax forms that asked me when the rental half of the house started being used as a rental, and it just happened to be the day I purchased it since there were tenants already living in that unit.
The 193.5k you referenced is already from after dividing the assumed building value in half, so yes it would be 100% business use.
