Rental Income - Built an ADU in California

The TurboTax for this area of taxation does not seem to work or make sense.  I'm trying to declare that I built an ADU (not bought it) and it's saying my depreciation available is almost the full price of building and able to take now, for just one problematic example.  Very confusing.  How can I get more help on just this section?  I've already tried to study everything online that TT provides on this topic, but not helpful yet.  Unlike other guided areas, the guiding on this one doesn't seem to make it all work.