Typical format of rview consis of three sections
Summary of the research; usually one paragraph 5 to 10 lines. This is the proof that the reviewer appropriately read the paper, and also indicate how the reviewer read the manuscript based on the reviewer’s expertise.
Major concerns; usually 3 to 5 short paragraphs in itemized format. This section is for fundamental questions for the reviewer. In case authors are not able to defend, major concerns can be treasons for rejection. In case the manuscript is quite satisfactory, this section may be skipped.
Minor concerns; anything other than major concerns. Mostly, revisions of inappropriate, insufficient or ambiguous explanations, correction of figures and tables, request to add reference, and any kind of suggestions to improve the manuscript are included.
Overall, the review comments should be enough specific and should not be too long, just necessary and sufficient.