Your question seems to be mainly about the expectations and customs at your institution. However, you can take inspiration from a very high level journal, ACM Computing Surveys (CSUR), that is accessible from the ACM Digital Library. At this level, there is no fixed number of lines for each paper. Rather, the papers are organized into batches (which make up chapters), and within each batch, a linear story is being told. Fundamental concepts are given much more space and some heavy papers that might be the last word on an algorithm or implementation might have only a couple of lines.
Be warned that coming up with a good story to summarize the research is quite difficult. It involves really understanding the research papers, but goes beyond it. You might imagine having to explain to a new student what this field is about. (The new student is intelligent, but does not know a lot.) If you can explain, then you have started to understand the field.