What this actually says, is that the FitBit on your wrist ("the tracker") will hold 7 days of detailed data in its little on-board memory, if this data is not downloaded, then the FitBit on its own will overwrite the previously recorded detailed data. In MT's case, this is not a problem as the battery likely would have died before overwrite of this detailed data could have occured. This really matters if the FitBit was left on the body, The FitBit, on its own, can't upload ANY data to the Cloud. Apparently, the memory of the FitBit on your wrist will hold up to 30 days of summary, non-detailed data.
Info from a FitBit CANNOT be uploaded to a FitBit corporate server for storage unless the FitBit first syncs with a web connected device that can upload the data, using the FitBit app on that individual phone which must be synced with the individual FitBit.
Once this data is uploaded to the FitBit server, the summary data will be held in the "Cloud", on the FitBit corporate server. I don't know for how long. This from where LE obtained MT's FitBit data, from the FitBit corporate servers, located on a server farm who knows where, but not on MT's wrist or CR's trophy box.
To summarize: FitBit wrist devices upload their info to the FitBit servers that form the Cloud only AFTER the wrist FitBit syncs with a phone or other synced device. (IT can't happen any other way.) Once uploaded, the data will be held in the Cloud. Interesting info. Thanks