earned $8.8 million in the US which is less than Transformers: Dark of the Moon but don't read into that. In the last three years, midnight releases went from uncommon to very common to now being 8 to 9pm night before releases for almost every single movie that comes out (the exceptions are rare instead of vice versa). The only reason studios don't plaster a Thursday release date on their movies is it could lead to confusion for matinee goers in the US.
In China the movie reached a new record for Thursday midnight previews with $3.5 million start and in Russia had a $5.5 million start. In Taiwan its had that country's best opening day ever at $1.4 million. All total its first night take in 22 overseas markets was around $30 million. That doesn't seem like much but bowadays a movie's success isn't graded by US box office results alone. The last three films worldwide total came to around 35% from the US and the rest overseas so Paramount is probably paying more attention to international numbers than domestic ones. If Transformers 4 hits the around the same 35 US/70 Int ratio than it will probably easily surpass a billion dollars even if its sputters out quickly in the US (which seems likely).
The movie remains on track for around a $100 million opening in the United States but I have yet to read an estimate on its worldwide take for the weekend but based on the international numbers it sounds like it will land in the $170 million range. Not a bad opening weekend for a budgeted $200 million movie. As for why does this matter? For Transformers 5 of course. The less successful a movie is, the less money a studio tends to want to spend on a sequel. If TF4 lands big than they will spend equal or bigger on the next. Success in this case at least a $1 billion worldwide take before it leaves theaters with a preference for over $1.2 billion so it surpasses Dark of the Moon's total. The bigger the first weekend, the more likely Hasbro's and Paramount's goals for the movie will be met.