Yes, that's correct. Max 6TB with 8.2.3 7-mode.
10TB capacity in DS4486/DS4246 is not supported with 8.2.3 7-mode, but with 9.x it is supported.
However, if you are happy with 8TB then just upgrade your 7-mode to 8.2.5 and you can work with 8TB disks.
If you do go ahead with 10TB in DS4486 enclosure with 8.2.3 7-mode: I have never tried it but I am guessing the system will recognize the disks but will be 'down-sized' to the max-supported disk size supported by that particular OS version type. Hence, you will lose out on capacity. Instead upgrade to 8.2.5 and use 8TB disks.