the prefix number of the configuration filename

15 Feb 2016


      Hi all,
I am very curious about the prefix number of the configuration
filename, such as 10-auth.conf
10-director.conf
10-logging.conf
10-mail.conf
10-master.conf
10-ssl.conf
15-lda.conf
15-mailboxes.conf
20-imap.conf
20-lmtp.conf
20-managesieve.conf
20-pop3.conf
90-acl.conf
90-plugin.conf
90-quota.conf
90-sieve.conf
90-sieve-extprograms.conf
What are those meanings of 10,15,20 and 90 ?
Please advise me and thank you in advance.
--
Best Regards,
Dogz