There is one problem that's been overlooked is that Emma didn't say what size canular she was given and nobody has actually asked!
In all the years I've been around pumps (a fair few now) I have many many times seen the same question asked by fellow pumpers how much to prime...
I have never seen any mention of any 'theory' to work out the prime for different sized canulars! as I know I would have remembered this, so I checked the 'bible' well pumping insulin to be exact if there was a theory then it would be located in this book but alas nope..
As we can see the 'theory' suggested actually works out quite different from what the manufacturer suggests... Which is 0.7 for the stills 13mm (which just happens to be the same prime for my tenderlinks made by rouche)
Now if I followed toms advice, then I would be over priming my canular by 0.5 units of insulin, for a lot of pumpers probably not going to make a huge difference by for me personally it would have quite an effect and very likely to cause a nasty hypo...
This is always the problem when answering questions in forums, sometimes we need to think, what the question is actually asking and how we may reply, do we give advice from what is recommneded or from our own experience!
In this case it should have been what the manufacturer says...