It will still work but you won’t see any extra space because of how the redundancy works, you lose your biggest drive in single-disk redundancy and your biggest two drives in dual-disk redundancy.
Wait for the lights to go green then swap out the 500G drive. At that point you should see additional space. If you are in dual-disk redundancy then you will only see 500G, the two 2TB get used for protection. In single disk redundancy you would see 1.5TB extra.