fnd_log_messages big in size but no row in table

We are using EBS version 12.1.3

select segment_name, segment_type, owner, tablespace_name, bytes from dba_segments where tablespace_name='APPS_TS_TX_DATA' order by bytes desc;

My query is showing FND_LOG_MESSAGES as the biggest object with 2398355456 bytes.

We run the purge log and closed system alerts concurrent request.

select count(*) from fnd_log_messages; is showing zero rows

select module, transaction_context_id from fnd_log_messages where transaction_context_id not in (select distinct transaction_context_id from fnd_log_transaction_context);

is showing no row returned.

I am very puzzled as to what is going on with this? Why would the table still have that big size?