I found another in the shed still in it's wrapper, I now have 4...
1 litre bottles
got half a bottle in the boot compartment for top ups.
RE topping up I read mine at work late afternoon and usually only top up if it's above half way, little at a time till it's on max or a smidge over pending on how heavy handed I am, I'd say in the 3 n so years of owning I've probably only topped up 3 times but even then it was only dribbles.
The manual states between min & max on a warm engine, but I've always gone by the old fashioned way of max on a stone cold engine, makes it a lot easier and more reassuring