I'd take that with a grain of salt because it doesn't tell the whole story.
Here's the whole truth: Unlike RtN, The Last movie's box office started off with a bang because--
1) It is the last Naruto movie and it was supposed to be canon linked to the manga. So the regular readers and even ones who loved Naruto for nostalgia flocked to theaters on the opening day.
2) It was the most heavily advertised Naruto movie ever.
3) It followed RtN which was quite a big hit. The popularity of the previous movie of the same franchise is very important to how the next movie will be received, especially on opening day.
Because of these reasons the opening day collection was 175 % more than what RtN collected in its first day. The collection by 3pm on its opening day was around US$4.3 million. By the end of third day, the collection was 156 % more than what RtN collected after its third day. So I'm guessing The Last's box office was already more than 8 million after 3 days.
http://www.animenews...lion-yen/.81916
Now, the collection is US$12.8 million apparently. So in the three weeks and four days that followed, its only collected about 4.5 million dollars. And this is telling.
Because RtN was not as advertised and did not initially have the same attraction factor that the Last had, it started off slower. The reviews were good , more people went to see the movie and the collection rocketed. So the main reason for RtN's success was because the plot was good, the characters were treated well and the movie got excellent reviews.
Contrast this to the Last. It was advertised heavily, it had a lot of pulling power and this showed in the opening day collection. But what happened afterwards..? The reviews were bad, many demanded refunds and the collection rate is gradually dropping. You only need to see the initial estimation to realize this. Because the movie was so well recieved on the first day, it was expected that the collection would top 2 billion yen. Its looking extremely unlikely that it will collect another 4 million in one month.
In a nutshell, RtN's success was down to the quality of the movie and The Last's success is down to the pulling power of 'Naruto' and the false advertising.