These are just subpoenas to produce information for the investigation, nothing more or less. You have to do subpoenas like this for medical records, some reporting, etc. This is likely a subpoena deuces tecum, which just requires the records/item/evidence to be produced to the party asking for it.
When I filled out subpoenas for the most recent case I did, it was for things like medical records, slides from the autopsy, photographs and other things like that. It still gave a date and time to produce those items at grand jury, although in reality, we arranged with the party we were subpoenaing to pick up those materials. It's different than what we think of as a grand jury proceeding - it's more of a court order to produce materials.
ETA: Yes, these subpoenas for materials had dates and times to "appear" - because there could be contempt filed if they weren't produced. It's not actually a scheduled court appearance in front of a grand jury. I don't believe that is the case here, either.