Beta 1.16 Ship average armour value calculation

I have been playing with fighter and gunship designs and have been trying to make designs more robust using anything other than speed. Since there are no shields, I am left with armour and hull points.

I made an assumption (based on the use of the word average) about average armour value during ship design; that it was calculated thus:

I happily built an excel spreadsheet - playing with all the armour types and hulls available. Then I went back to the game to try out some of my theories.

However, the ship design tool seems to be calculating average armour thus:

Is this correct behaviour? It seems consistent across all hull types - but I wanted to be sure it wasn’t a bug. If it is correct behaviour, then I’ll just have to tweak my spreadsheet and accept that armour isn’t as strong as I expected.