In LINSTOR server versions before 1.26.0, configuring over provisioning of a storage pool backed by a thin-provisioned LVM volume or ZFS zpool was based on the amount of free space left in the storage pool. Starting with LINSTOR version 1.26.0, you have the option to limit over provisioning of storage pools by using a second strategy, based on the total capacity of a storage pool.
An updated version of the LINSTOR User’s Guide has a section about this and shows you how to configure the relevant properties.