Quotacheck doubled quota in Virtualhost with chroot jail


I’ve noticed tha the Virtualhost quota is doubled after a quotacheck via Virtualmin tool.
In this way a lot of Virtualhosts are overquota but the effective homedir size is half the quota indicated by Virtualmin!

In these Virtualhosts i have enabled the chroot jail.

In Virtualhosts where chroot jail is not enabled, the quota count match the homedir size.

What i am doing wrong?

Thank you for you help/suggestions.