Pamela wrote:
On 14:58 14 May 2021, Peter Able said:

Surely the only rule is that it is discourteous to confirm back a
number NOT in the format first spoken. E.g. 23 93 73 confirmed
back as 239 373 !

It may seem so but digit grouping that's easier to recall (which is
what some people like to emphasise) is not the same as conventional
digit grouping when you want to confirm you've understood a number.

For example, Three Mobile customer service is: 0 33333 8 1001

That may be handy to remember after you have heard it enough times but
for a simple one-off confirmation it's messy because it breaks the
usual rhythm when speaking such numbers.

Nor can you easily confirm it fits the usual landline format of 5+6
digits.

I prefer: 03333 381 001.

Chunking comes with it, some RLE (run length encoding)
by the operator. You can be remembering the first cluster
as "zero and four threes". There is a tendency to chunk such
that repeated digits are at the beginning ot the end of the
chunk. As if doing it as "an RLE bit plus a sound".

Humans are both crafty... and lazy.

Paul