You know, thinking a bit more about this, it would seem likely the vast majority of docs Snowden obtained would be NSA, not GCHQ, and it would also be unlikely Miranda would have been traveling with the whole Snowden archive in any case.
The UK detention of Miranda in transit occurred months after the intial Greenwald/Poitras disclosures, so, logically, it’s more likely only a portion of the entire archive was being transported, maybe because Greenwald and Poitras were coordinating and working on a GCHQ-related story. Miranda was also found with, and had taken from him not just the external hard drive with “58,000” UK intelligence docs, but also a laptop and some thumb drives.
So, guesstimating on just that thin basis, the total document count might very well be much more than the “up to” 100K I suggested. I’m thinking now maybe 150K to 250K total [NSA and GCHQ, etc.] documents turned over to G/P by Snowden. Maybe. But, again, not 1.7 million. Neither Greenwald or Poitras seem to have noted anything other than “tens of thousands,” ambiguously enough.