edit this file
/var/www/html/webmail/inc/config.php
look for
$quota_limit
and set it to 0
then save and exit, now, uebimiau will not show quota and will be based on da quota.
BUT, ive notice a bug on this, if u set 0 as quota u will lose the page 2,3,4,5, option in email (hope they solve soon), so, i sugest u to put 10000 as quota (10MB) but this will be a fix value for everyone (so if u put 20mb in da, will always be 10mb via uebimiau).
sorry for poor english, hope it help
regards