How to calculate Mandays for half-yearly return under the Factories Act?

Dear Sir/Madam, Please help me. How to calculate Mandays under the Factories Act? In my Company, we engaged contract labour 150 everyday and company workers 300 everyday. But Daily attendance is like sometimes contract workers 145, 130 ...etc and company workers 290, 295, 280 ...etc. How to calculate Mandays for half-yearly return (January to June) as attendance is different every day. Please help.

Dear ABC,
first of all do not hide your identity, what we will understand when you are hesitating to put your own name.
second for Mandays calculation make the average men on every month. and same for six months.

Help Me to know About Mandays calculation and Manhours Calculation for annual return..In my factory there are 500-600 employees every month working