Mailbox disk usage is displayed incorrectly

[WNTParallels]

In Plesk 10.4.4 (up to date) the disk usage of email accounts shows a maximum of 2GB. Even if the account uses more disk, the displayed disk usage is 2GB. In the psa Database, de Disk usage is correctly, so I think the error is in some php file. This is in the "Mail" tab of any Subscription.

Thanks in advance for your help.