VW LT35 Coolant Capacity Confusion

Can anybody who has totally drained, flushed and refilled the coolant system on their LT35 give me a hand here? I've flushed several times with water, and now allowed to drain from the radiator cap and the heater hose and the pipe it connects to, also clamping the hose and flushing / draining to get all of the coolant from the block. Now I have begun to refill it seems as if I have got about 40% or so of the coolant out of the system - have put in 3 litres of G12 antifreeze and 2 litres of water, run it for 5 minutes, and it is seemingly 'full'. Workshop manual states capacity of this model (5 cylinder, 2.5 109bhp engine type ANJ) as 11.5 litres. There is clearly something I'm missing here, any help would be appreciated as this is the first time I've done this. Going back outside now to drain and collect the mix I have just put in and see if I can't coax something more like the official capacity out of the system.