GSTR-3B late fees 500/-

i want to file GST returns(GSTR-3B) from june 2019 to july 2020. My query is. late fees 500/-per return or per month? Total turnover 15 lakhs.

Say, June-2019:

i)500/-per return(total june month) OR

ii) 500/-*13 Months=6500/-