Atrax Fountain pen confusion

[Garno]

I have run into a problem before I even start with the Atrax pen.

This time I decided to read the instructions before I do anything and have ended up totally confused.
The instructions say to drill the larger blank 12.5mm and the short blank 10.5mm, however the shorter tube is 12.5mm and the larger 10.5mm.
When the instructions tell you the length are they actually referring to the diameter? or do they mean laying the tube down and measuring from left to right (that would make more sense). I am getting confused by length meaning diameter.

The short tube is the fatter one.

https://www.turners-retreat.co.uk/files/pdf/pdf1087.pdf

 

[flexi]

I prep the same way for every pen....
Lay the tubes on the blank... Mark the lengths + a tad, cut and witness mark it (grain alignment later). Measure the tubes, measure the tubes, drill with nearest bit, then glue up.
Instructions are just to work out where the bushes go

 

[flexi]

I have downloaded and read the instructions, although not very clear it does say 'cap tube' 12.5mm so is correct