Just that typically our cars will download a lot of data for the several days prior to an OTA update showing as available in the car or app.
The other possible reason for a big download would be to update offline maps, which does happen from time to time and has nothing to do with an OTA software update.
If there is neither an OTA update in the works, nor an offline maps update, our cars typically download very little data. So this looks like either a maps update is taking place, or that an OTA software update notice will appear on our cars soon.