Hi Yomo,
Don't worry. HIKNOS are just the letters given to the different verbal question types as noted by IPS publishing. We call them Types 1 to 21. IPS just uses letters instead of numbers.
The reason HIKNOS came about was that one eleven plus site advised that for certain areas you don't need to revise HIKNOS types. But actually, in the past, certain HIKNOS questions did actually occur in those areas. That's why we have always said to learn all of the 21 question types for verbal reasoning. It won't take your child long to learn these extra six types and even if they do not appear it is still good mental exercise to do them.
Hope this helps. If you want to know how our question types relate to IPS questions then there is a conversion chart here...
IPS to Chuckra Types