This iMac comes standard with 256GB of SSD storage,¹ but it can be configured with up to 1TB of storage, giving you more space to store your documents, photos, music, and apps, as well as extensive video libraries and large data files.
Note: Storage is not user accessible. If you think you might need more storage in the future, it’s a good idea to add it now.
1.1GB = 1 billion bytes and 1TB = 1 trillion bytes; actual formatted capacity less.