The maximum number of cache objects on the ProxySG depends on the amount of physical disk available on the unit, which is 2,292,607 per disk. If the ProxySG has two physical disks, the maximum number of cache objects is 4,585,214.
The amount of available disk space can be checked in the Management Console at Maintenance > Systems and Disk > Disks.
The maximum number cache object supported by the unit can be checked in the Management Console at Statistics > System > Resource > Data.
The only option to increase the maximum number of cache objects is by upgrading the ProxySG to higher model which has more disk space. If an upgrade kit for the ProxySG model, an upgrade which include additional disk will enable more effective maximum object cache.