Hypertable_size() does not return correct number


We use TimescaleDB as our storage in our project.

We have a hypertable organized as daily chunks and we have a functionality to dump data from this table to csv. This dump functionality works over COPY API and creates one CSV per chunk of this hypertable.

The issue is, when I run hypertable_size() function on this hypertable it shows a size of around 1,6 GB but if we export the data from this hypertable to csv via mechanism I mentioned above, it gives CSV data of around 3 GB. We checked character encoding of DB and the CSV files, all are UTF-8. Is there a point we can check with the DB?

I cannot provide much exact detail due to information security but in case you need information, I can provide mocking some parts.

Thank you in advance.