Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| Release | # of discs | Region 1 | Region 2 | Region 4 |
| --- | --- | --- | --- | --- |
| Series I | 2.0 | 25 February 2003 | 4 November 2002 | 3 December 2002 |
| Series II | 2.0 | 25 February 2003 | 10 February 2003 | 1 April 2003 |
| Series III | 2.0 | 3 February 2004 | 3 November 2003 | 18 November 2003 |
| Series IV | 2.0 | 3 February 2004 | 16 February 2004 | 9 March 2004 |
| Just the Shows Vol. 1 Series 1-4 with no extras | 4.0 | N/A | 18 October 2004 | 12 November 2004 |
| Series V | 2.0 | 15 March 2005 | 8 November 2004 | 1 December 2004 |
| Series VI | 2.0 | 15 March 2005 | 21 February 2005 | 6 April 2005 |
| Series VII | 3.0 | 10 January 2006 | 7 November 2005 | 1 December 2005 |
| Series VIII | 3.0 | 2 May 2006 | 27 March 2006 | 20 April 2006 |
| The Complete Collection Series 1-8 with extras | 18.0 | 5 September 2006 | N/A | N/A |
| Just the Shows Vol. 2 Series 5-8 with no extras | 6.0 | N/A | 2 October 2006 | 3 November 2006 |
| Beat the Geek (Interactive DVD quiz game) | 1.0 | N/A | 23 October 2006 | 3 March 2011 |
| All the Shows Series 1-8 with no extras | 10.0 | N/A | 10 November 2008 | N/A |
| Back to Earth | 2.0 | 6 October 2009 | 15 June 2009 | 17 December 2009 |
| Just the Shows Series 1-8 with no extras | 10.0 | N/A | 9 November 2009 | N/A |
Question:
How many DVDs where were in the complete collection series 1-8 with extras?
Answer:
18.0