Q: What is the minimum number of comments to be included while proofing my paper?

I don't think there is any specification about the minimum or maximum number of comments can be included during proofing. If you see errors, you will need to correct them. You should go through the entire article carefully and look out for errors that the copyediting team may have missed. also look out for inconsistencies. For example, the word "email" may be spelt as "e-mail" at some places and "email" ( without the hyphen) at other places. Ideally it should be spelt in any one way throughout the manuscript. Also, check for consistency in abbreviations, formatting of references, use of numbers, capitalization, etc. Feel free to put in as many comments as you need to. The number of comments is not important: what is most important is that your manuscript should be error free.