What is the capacity?
The capacity is how much it holds.
I don't know why a figure matters unless you are wondering why your 1.5 litre cooling system takes
4 litres.
The KDX spec sheet doesn't list a capacity for the cooling system.
The 'bleeders' mentioned are plugs/bolts, not bleeders in the sense of threaded petcocks (as you find on automotive radiators/cooling systems). You will find one on the kdx head in the vicinity of the coolant hose nipple.
It's important to have no air in the coolant system (thus the 'bleed' part). It is possible for such entrapped air to block coolant movement.
That's a bad thing! ;)
A good primer on different types of antifreeze is
here.
The most important part of it is at the bottom: Use what is recommended, change it when you should.