Garage accidentally Included in Sqft???

[Austin N.]

Hello BP! I am currently in escrow on a duplex in LA County. It consists of a front house, and a back unit attached to an unfinished garage (all built in 1930s). The listing/ LA county assessor lists the back unit at. ~650 sqft. However, I recently inspected the property and its 350 sqft at most. All work has been permitted and I have confirmed with the city. Conveniently, if you were to add the garage sqftage to the back unit, it would be right around the claimed sqftage (~650). 

Is it possible the unfinished garage was incorrectly added to the sqftage? What would be the process for fixing this (if I should)? Anything else to worry about? If it matters, I am looking into converting the garage to an ADU.

Thanks!

Austin