How is registered tags quota calculated?

From PTAGISWiki

The registered tag quota for a user is displayed at the bottom of the My Registered Tags page. The jsp calculates the quota and the usage with this code:

    nQuota= ((Long) session.getAttribute("reg_tags_quota")).longValue();
    nUsage= (int) Math.floor(oRegTags.getTotalTagStorageSizeInBytes(userName)*100/nQuota);

The oRegTags object has this code:

    /**
     * Retrieves the sum of the tag counts in the user's tag groups.
     * This method has been updated to return the actual number of tags,
     * rather than their size in bytes!
     * @param userName the name of the user
     * @return the sum of the tag counts in the user's tag groups
     */
    public int getTotalTagStorageSizeInBytes(String userName) throws SQLException
    {
        Connection oConn= null;
        int nTagCount= 0;
        try {
            oConn= m_oDBConnection.newConnectionB(Connection.TRANSACTION_READ_UNCOMMITTED);
            oConn.setAutoCommit(false);

            String sCmd= "SELECT SUM(num_tags_contained) FROM mrt_tag_groups WHERE user_name=?";
            PreparedStatement oStmt= oConn.prepareStatement(sCmd,ResultSet.TYPE_FORWARD_ONLY,ResultSet.
CONCUR_READ_ONLY);
            oStmt.setString(1,userName);

            ResultSet oRS= oStmt.executeQuery();
            nTagCount= oRS.next()? oRS.getInt(1): 0;
            oRS.close();
            oStmt.close();

            oConn.commit();
        }catch(SQLException e){
            oConn.rollback();
            throw(e);
        }finally{
            if (oConn!=null){ oConn.rollback(); oConn.close(); }
        }
        return nTagCount;
    }