What is meant by "little do they believe"?

Imām Ibn al-Jawzī (d. 597/1201) summarized the scholars' opinions in his book "Zād al-Masīr" as follows:

1. It means few among them believe. [Ibn ʿAbbās, Qatādah]
2. They only believe in a small portion of the scripture they possess.
3. They do not believe at all, neither a little nor a lot. This is mentioned by Ibn al-Anbārī. He explained that this is based on the linguistic habit (lughah) of a group of the Arabs who will say, "Rarely have I seen someone like this man," meaning, "I have not seen anyone like him."
4. They believe for a short period of time, as in Allah's statement: "Believe in what was revealed to those who believe at the beginning of the day..." (3:72) This is also mentioned by Ibn al-Anbārī.
5. The meaning is: their faith is little (i.e. weak). This was mentioned by Ibn Jarīr al-Ṭabarī.