The SSD enclosure in the Mac Mini M4 Stand & Hub with SSD Enclosure runs at up to 10 Gbps (USB 3.2 Gen 2). Even though the Mac mini's port is Thunderbolt 4, or Thunderbolt 5 on M4 Pro models, the enclosure itself connects at USB 3.2 Gen 2 speeds, so 10 Gbps is the maximum for the built-in drive.

NVMe SSD speed ratings are usually measured with the drive installed directly inside a computer. In an external USB 3.2 Gen 2 enclosure you will see lower numbers, and that is expected.

To get the best speeds:

1. Format the NVMe drive as APFS or ExFAT.
2. Connect the hub to a USB-C port that supports 10 Gbps or faster (USB 3.2 Gen 2, Thunderbolt, or USB4).
3. Avoid running heavy read and write tasks through the other ports at the same time.