What does get reported in fmol/L is HCV CORE ANTIGEN. This is a test like PCR (in that it is looking for and counting how much virus it can see).
Here is a paper: http://www.ejmm.edu.eg/beta/images/articles/April_2014/67-74.pdf
In the paper it says:
Based on this equation, it was possible to calculate that 3 fmol/L of total HCV core Ag is equivalent to 263 IU/mL HCV RNA
So that would be 1 fmol/L to 90 IU/ml of HCV RNA – call it 100
So your 673 represent a viral load of about 60,000