To build on what @miregan was saying, In your PreStage Enrollments, the devices under the "Scope" section, are just a list of devices that are tied to your MDM server (Jamf Pro) in DEP, that Apple has a record of. These are devices that are capable of being enrolled with DEP via Jamf Pro. When they say "Assigned" like the example above, it means that when that device is going through the initial setup screens, and calls out to Apple's DEP servers, it will see that it belongs to a a PreStage Enrollment, and will prompt you to configure the device (enroll). Until the device is actually enrolled, you won't be able to manage the device. If you have already gone through that process, but the device does not show under the Computers section in Jamf Pro, it may not have enrolled properly.