Administration > Single Sign-On > Users and Groups), the interface displays a maximum of 200 users or groups:VMware vCenter Server 7.x
VMware vCenter Server 8.x
This is expected behavior.
vSphere Client UI displays only 200 users/groups initially, but there is now an option to search for any particular user/group.
If you want to have the list for all users/groups, you can get it from the PowerCLI commands:
Get-SsoGroup -Domain "vsphere.local"Get-SsoPersonUser -Domain "vsphere.local"Install-Module VMware.vSphere.SsoAdmin).