this comment is not exhaustive, so make sure to do more research. make sure to mark the ACC unit box in the improvements section. I would include info about it in the improvement section extended comments describing the finish out and entrance. it sounds to me like the liveable area of the ADU is entirely separated from the actual square footage of the main residence. if the garage is in between them, they’re separate so the additional square footage can’t be included. you can still comment the square footage (and you should) as well as to have that part sketched out, and mentioned in the bottom of the grid in the sales comparison section to make proper adjustments. Mention if accessory dwelling units are all that common or uncommon, and comment on the marketability. find at least one other house as a comp with an ADU, or workshop or swimming pool or something that sets it apart from the houses without. You may really need to do the income approach on this one as well since a lot of people would decide to rent that out. Hopefully this info will get you started off