Theory:

 I wrote in large block letters:

CATCHING A CROOK

Expert Detectives: Nishad and Maya Pandit
By Appointment to the Whole World

     Then I began writing. About half an hour later, I turned towards Seven who was lying on his tummy, chin cupped in his palms, reading comics. “Want to hear what I’ve written?” I asked.

     He looked up questioningly. “I’ve listed all the facts we know about Mr Nath which might help us to trap him,” I said. “Want to hear?”

     Seven nodded.
Explanation:
 
Maya decided to make the most of the day by gathering the information relevant to the investigation and putting it down on a sheet of paper.
She began by giving a heading for her report: "CATCHING A CROOK". She wrote the words in large block letters. She also gave a subheading to the report she was preparing: "Expert Detectives: Nishad and Maya Pandit". It was followed by a tagline: 'By appointment to the Whole World'.
 
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Maya was putting down the facts on a paper

The heading and its subheadings reveal more details about the characters. Foremost, the heading reflects Maya's perspective of Mr Nath's situation. Despite knowing that Nishad doesn't share her belief, she establishes her stand that Mr Nath was indeed a crook, declaring that the main agenda of their investigation was to find ways to expose and catch him.
 
The subheading is vital because we learn, for the first time since the beginning of the lesson, that "Pandit" is the surname of Maya and Nishad. Furthermore, she calls themselves the "expert detectives". This is also one of the two instances in the lesson where its title appears.
 
Despite their differences in opinion, Maya is not someone who believes that she is a better detective than Nishad. This could be evident from the manner in which Maya had positioned their names in the subheading. Had Maya been self-conceited, it is likelier that she would have begun with her name rather than Nishad's. Hence, it is possible that Maya distrusts Mr Nath for reasons of her own and not because she looks down on her brother.
 
The tagline, on the other hand, exposes the childlike qualities of Maya. Though an elder sister to Nishad, Maya is only ten years old. She is as young as any child of her age could be. The tagline reveals how she innocently believes that her and Nishad's work would benefit the whole world.
 
After giving the heading to her report, Maya spent about half an hour formulating the body of the report. While Maya was writing, Nishad was on the bed, lying on his tummy, with his chin cupped in his palms, and was reading comics.
 
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Nishad was reading comics

Once she was done, Maya requested Nishad to listen to what she had written. He looked up questioningly, unaware as to what she was referring to. She then explained about her report and told him that she had listed all the facts they know about Mr Nath. She also added that the facts might help them to trap him.
 
Nishad nodded, indicating that she could continue reading the list out.
Reference:
National Council of Educational Research and Training (2007). Honeycomb. Expert Detectives:Sharada Dwivedi (pp. 126-132). Published at the Publication Division by the Secretary, National Council of Educational Research and Training, Sri Aurobindo Marg, New Delhi.