It's stupid to think that the difference between 350k and 500k is immaterial, especially for a company which struggled to hit the low end of that range the last 2 years.
Tweeting that they definitely would hit the high end of that range, i.e., 500k, i.e., almost 142% of the low-end of the range, was a specific statement about Tesla's capabilities intended to narrow the range of the earlier statements in the interview. Ergo, the tweet was material information and it was reasonable for investors to interpret that Tesla would hit 500k by the end of the year, because it was tweeted by the CEO himself. The clarification about it being a pro-rated (i.e., annualized) number was not provided until much later. (And legally that makes all the difference.)
Tweeting that they definitely would hit the high end of that range, i.e., 500k, i.e., almost 142% of the low-end of the range, was a specific statement about Tesla's capabilities intended to narrow the range of the earlier statements in the interview. Ergo, the tweet was material information and it was reasonable for investors to interpret that Tesla would hit 500k by the end of the year, because it was tweeted by the CEO himself. The clarification about it being a pro-rated (i.e., annualized) number was not provided until much later. (And legally that makes all the difference.)