Laravel log max file is not working

I am using laravel 5.2, I just deployed my code on server. I am using laravel logs on the daily basis and so in the confg/app.php i added these two lines

'log' => 'daily'
'log_max_files' => 15 

But it is not keeping the logs of 15 days. It is always keeping the logs of last 5 days only which is default file size. Am i missing something to add..?

via Chebli Mohamed