Yes the actual record content on the network isn't huge at the moment but the firehose doesn't include blobs (images and videos) which take up significantly more space. Either way, yeah it's pretty lightweight. Total number of records on the network is around 2.5Bn in the ~1.5 years Bluesky has been around.
I aggregated some stats when we hit 10M users here - https://bsky.app/profile/did:plc:q6gjnaw2blty4crticxkmujt/po...