Finding HVAC Calculations for New Construction

I'm trying to find the HVAC calculations for a newly constructed home I'm buying in Southern California. My house is ~2,900 sq ft, 2 stories, and is being serviced by a 3 tons AC unit. Everything I'm reading online is pointing me in the direction this is undersized and the construction company for the house says I can find the calcs online if I distrust them. Any thoughts on how/where I can find them? I've been going onto the City Building Permits site, but it doesn't look like any documents (only inspections) are embedded there

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