[exim] question about quota

dear fels

i would like to ask something about exim quota

i have an exim system based on sun solaris...
the system based on mbx format mailboxes

now if i used the quota option in the appendfile transport

1- does the quota applied only on the mailbox file only or the summation of all files on the same ownership?!

2- if there's a mail delievery while pop session...where suppose that lock the file system (the mailbox size then while 0 bytes)
does it wait till the lock is off....or it deliever the mailbox based on the size

thanks for reply
mostafa