I think the reason Musk and Tesla are very sensitive about production numbers right now is that they want to hit their 200k electric car production number at just the right time. The way the $7500 federal tax credit works (and I am pretty certain this is right. Happy to follow a link to the actual law) is that after a company makes 200k qualifying vehicles, for the rest of that quarter and the quarter after that people still get the tax credit. So depending on when they hit the 200,000th car, the full tax credit will last between 3 and 6 months. Tesla would like to get the Model 3 production ramped up to a high level but not hit the 200k total production until right after the start of a quarter.
It looks like they are going to do just that. Tesla is very close to 200k this month and that is probably partly why they shut down to "improve production rate". Slow down production in June to not hit 200k until after July 1. They have also been playing with exporting more cars to hit the 200k number at just the right time.
Having the maximum 6 months instead of the minimum 3 months will be a lot of extra cars/people getting the tax credit. If they average 6000 cars a week over that time (12 weeks x 6000 x $7500) that is an extra $540 million.
Then the tax credit goes in half for the next two quarters and in half again ($7500/4) for the next 2 quarters.
Seems a bit strange for the law not just to say the credit extends for 6 months after the 200,000th car is built, but who knows how such laws get crafted.