Hello @RGalvin , Thanks for using Microsoft Q&A Platform.
The limit of 20 files is per assistant/thread and I believe it might include files attached to messages but please try. If you have multiple assistants, the limit of 20 files applies to each assistant separately. I hope this helps.
Regards,
Vasavi
-Please kindly accept the answer and vote 'yes' if you feel helpful to support the community, thanks.