Detects only one disk

Hi. I have MyCloudEX2Ultra 2-Bay NAS, with 8Tb. That’s two disks with 4Tb each. But when I enter the config page it only detects 4Tb of free space.

When I go to Storage/RAID it only appears one volume, but when I go to Disk Status I can see the two drives healthy.

What should I do?

Thank you!

Ok, I think I have to change the RAID mode to Spanning.