Hi, I think I put about 3 litres through when I flushed mine through, just kept bleeding it until it ran through clean. It used more than expected (had to go out and get some more)
With clutch its about 1.2 litres although VW suggest in their service schedule, putting 500ml through each bleed nipple, so that would make it 2litres for the brakes and another 500ml for the clutch.
In reality though, 1.5 litres is plenty for a complete change.
However, use a 'sucker' (those basting suckers work well) to empty the reservoir first, re-filling with fresh fluid...otherwise your first bleed (furthest away from master cylinder) will be receiving old contaminated fluid (even if it does look clean it may contain water).