Diskspace not correct displayed - 51gb Used and 1,6gb shown in the user list

in my user list

I look in my user list and next show me the used diskspace, but some users has 50gb gb and some Users are shown with 1,6kb … not with 51 Gb. some Users with 30gb has displayed with 30 gb.

Nextcloud version (eg, 12.0.2): 13.0.5
Operating system and version (eg, Ubuntu 17.04): Ubuntu Managed Server
Apache or nginx version (eg, Apache 2.4.25): newest
PHP version (eg, 7.1): 7.2