Am I being dumb ?

[Fivetide]

I bought some :

BLACK MALLEABLE IRON REDUCING PIPE FITTINGS BSP - SOCKET, BUSH, TEE, HEX NIPPLE
( 111520014759 )

Fitting Type: REDUCING BUSH

Size: 1/2" x 3/8"

When they arrived I was surprised my 3/8" male threaded pipe didn't fit ?
So I emailed the vendor and said although you have 1/2" to 3/8" stamped on the Bush its actually measures 14.1 which I think is 9/16 0.5625 or 14.2875mm well near enough.
Anyway I emailed the guy and this was his reply

hi David, there is no such size as 9/16" , the fitting is correct just check . (there is sizes cast on fitting one side of hex part)
1/2" X 1/4" bushes have a inside 11mm if any better for you.

Here's me thinking 1/4" was 6.35mm ?

I'm confused

Pic attached



As Robin has stated an interest in "having fun" I withdraw my earlier request...your all now free to continue with lessons and raucous finger pointing !! :P

Hold on indeed, you ask if you are being dumb and then say, "No need to answer" ???

Where's the fun in that? :)