if i won't give the exam of April than is my rank will come in accordence to number of students appeared in jee over all

Hey there hope you're doing well.
If you are not willing to appear for April session of JEE MAIN it's fine . Your percentile will be decided by no of students appearing for January session in your shift and that's your relative score that matters here.Once your percentile is decided and recorded it will contribute for your AIR.
Thank you hope this helps you!