I figured it out. There are no instructions at all when it comes to the BTA mount. None. There's not even a mention as to what it is. Had I not seen it in this thread already I'd have no earthly idea what it was.

Additionally, the half a page instructions for the whole setup (yes, that's all you get is half a page) include this line about the armrest spacers: 4. Aerobar bracket riser kits are included to increase the armrest height. Choose the amount of height increase needed and corresponding bolts using the attached chart.

There's no attached chart. There's like 10 different hardware bolt sets that are clearly marked but there's no chart. It would have been nice for some mention of what the base stack is with the tilt hardware. I had to figure that out. It's 20mm for those wanting to know. So I put on another 20mm spacer plus the 5mm for the BTA bridge with a slam stem. So I needed the 45 mm hardware bolt set. Once again, it would've been nice to have that info in front of me so I don't have to figure it out on my own.

A to A+ grade for quality of product. Super nice bar and stem system.
F for instructions. We are talking about cheap, Japanese toy level of instruction manuals for an aerobar system that costs $1,200.

Others should follow TriRig's lead on this. Their instructions on their website for the Alpha X are near perfect.