I think you mean JLPT, which is the Japanese Language Proficiency Test. It's split up into 5 levels, N5 being the lowest, N1 being the highest.
Shiritori Cat is telling you a word that isn't in Renshuu's JLPT vocab lists was played. Renshuu's lists are a best guess at what might appear on the JLPT, but there's no guarantee.
What do you mean by highest and lowest for N5, and N1
Exactly what I said in my post. The JLPT is split into 5 levels. N5 is the lowest level of the test. It's for beginners. N1 is the highest level of the test. It's for people who have studied Japanese a lot. Most people don't take the test at all because it's expensive. Those that do usually only take the N1 because the certification is useful for work. Some people do take the lower levels of the test to measure their own progress, though.
