In any case, the data is "whatever needs to be logged".
And it's not "server logs", which is what I'm interpreting from your comment. Scribe transports most data at Facebook to be processed by real-time systems (e.g. Puma, Scuba) and also "batch systems" (data warehouse). So, it's quite a lot, being "the ingestion pipe" for Facebook.
Does this answer your question? :-?
Puma: https://research.fb.com/publications/realtime-data-processin...
Scuba: https://research.fb.com/publications/scuba-diving-into-data-...