If you mean how do I know what % of the 400K reservations were people wanting AWD or Performance rather than LR or SR, I have no idea. From a few posting on TMC, I'd read that many high margin cars were bought by new customers not existing reservation holders. At the time reservations opened, the number of variants and order of introduction were not public, so I don't know how clearly even Tesla knows how many reservation holders won't buy M3 until a 35K base version is available. Nor what % had to have an AWD or Performance.
I suspect many who reserved did not have one fixed amount they might spend. Leaving that up to what Tesla features/performance Tesla would offer at higher price points, down the line. I would guess the initial demand for high margin cars was the intersection of people excited about EVs and those who own high end sedans or aspire to buy them. I thought that word of mouth and drives from friends who purchased the more expensive versions would lead to plenty of additional sales after the early surge. I expected some slowing of AWD and P sales, but not so steep that making lower cost versions available would come to be viewed by Tesla as critical path to robust profits after the excellent Q3 results.
