Dear Abhay
Just go throug the below from Kerala Factories Rules:
Mandays worked should be the aggregate number of attendance of all the workers, covered under the Act, in all the working days. In reckoning attendance, attendance by the temporary as well as permanent employeed should be counted, and all employees should be included, whether they are employed directly or under contractors ( Apprentices, who are not covered under the Apprentices Act, 1961, are also in be included).
Include all employees (covered under the Workmen's Compensation Act, 1923) whether permanent or temporary who would, in the case of accidents, be eligible for compensation under the Act and for whom a return is required to be furnished. Number employed should be shown even in there are no payment of compensation to report.
From all the above what I am concluding is any work which we suppose to conduct inside the factory after getting license will be governed by the Act... Even if its a civil construction inside factory premises... Hence you need to take license of maximum number of employee, who can work even for a day in your factory...
In our factory the license is for 2500 employees and where in normal working days the manpower is around 800 only... We take this license in view of shutdown also, as during shutdown 1000 or sometimes more extra manpower coming to work...
I hope now your doubt is clear... And I hope I am right... If not, request to all who reads this, just to correct me...