Inventory at end of Q4-2022 was 70,249 being 13d of deliveries (i.e. sales, at 75d/qtr)
Q1-2023 increased inventory by 17,933 bringing it to 88,182.
88,182 / (422,875 / 75) = 88,182/5,638 = 15.6 days of sales, i.e. rounds to 16d
Models S/X
Cumulative production: 628,961
Cumulative production: 610,844
Calculated inventory: 18,117
Model 3/Y
Cumulative production: 3,538,732
Cumulative production: 3,461,834
Calculated inventory: 76,898
Total calculated inventory: 95,015
Actual inventory is a bit less because a few cars are totaled during shipping or whatever and never get delivered. I also don't know how they count cars they crash test or otherwise use internally without ever selling them. In theory those shouldn't count as production, but maybe Tesla counts everything with a VIN. Also note that Tesla's early production and delivery reporting was a bit haphazard, so there are small errors/estimates in the S/X numbers. Shouldn't be off more than a couple hundred.
The P&D report is accurate for production, but off a little for deliveries. I update my numbers with deliveries from the earnings report once it comes out.
My calculated days of inventory is usually ~1 day higher than Tesla's. Perhaps they don't include demo cars in inventory or something (they do eventually count as deliveries). A few years ago it was more random, sometimes we'd match and sometimes our numbers would differ by 2-3 days. I don't know why.
Especially when considering that includes stock in transit on ships as well as rail and road transport, plus show rooms, plus holding centres. For example that would be only (say) 8-10 shiploads in total. So 4 ships at sea; 2 shiploads in factory parking lots awaiting loading; 2 shiploads at unloading sites; and 2 shiploads spread around (750+) showrooms and delivery centres. The point being pretty quickly you can very reasonably account for 88k units.
Historically at EOQ there were no cars on boats, at shipyards/railyards/etc. That's changed lately w.r.t. China, e.g. some of the 13,870 cars exported from Shanghai in December were delivered that month in nearby markets but many were not. It'll be a few days before we know the export number for March.
Fremont still builds west coast cars the last couple weeks of the quarter, kind of a mini-wave. I don't see more than a few days of true "in transit" inventory for Fremont. I presume Austin (for now) and Berlin are similar.