[Rollo]

that means that for each 400kt of hull space one component that has Point-Defense ability will be added. Note that this is always rounded down, but a minimum of one component will be added. So that results in:
1 component for hulls from 1 to 799
2 components for hulls from 800 to 1199
3 components for hulls from 1200 to 1599
and so on...