You do realise the 5.5 thing is a joke right? It's something called Goroawase which is wordplay between numbers and phrases, all of which can be pronounced differently based on the same spelling
"Vi" is one of the several romanised way of writing 5 when translating Japanese
Vi Vi literally means 5 5
It's a JOKE about her name - it's just as canon as Luffy's attack range in the EB saga being as large as 10 Gomu Gomus and Robins range being 200 Hana Hanas. It's nonsensical and meaningless.
There is a very interesting Goroawase theory for the Strawhats and their devil fruit powers though which does relate to this thread - it was brought up by an audience member in another SBS soon after Brook joined. Some phrases/syllables can match multiple numbers so the order can actually be played around with to fit someone like Kuma or Monet into the narrative but this is something Oda has obviously designed. Anyway I think a visual representation makes more sense of it
As:
Luffy has Go(5) Mu(6) --> 56
Chopper has Hi(1) To(10) --> 110
Robin has Ha(8) Na(7) --> 87
Brook has Yo(4) Mi(3) --> 43
and San Ni Go ("Sunny Go!") = 325
325 - 56 - 110 - 87 - 43 = 29 AND 2 and 9 are the only digits left within 1-10 which convinces me this is the right order.
Yu Ki (Monet)
Ni Kyu (Kuma)
Fu Ku (Kinemon)
All have these fruits that fit the pattern - so you can see how while there's something there, it's quite meaningless to really dig into the detail but I will say Yamato also fits this pattern.
2 can be any of the following:
Fu, Ni,
In, Tsu, Ki
9 can be any of the following:
Ku, Kyu, Ko Yu,
Nu, Na
Inu Inu no Mi...
If you're going to focus on Goroawase, well, the answer is staring at you in the face.