Diet By Curmudgeon In The Crossword Centre

[Matakari]

Good morning, I’m fascinated by Curmudgeon’s DIET in the Crossword Centre (Crossword Centre Prize Puzzle August 2021 ), but am somewhat baffled by this part of the preamble: “An extra letter not entered in the grid is generated by wordplay in every clue.” How does one determine the extra letters? For example I have answered the following:

ACROSS:
1 Mother's expression of grief returning Jeddah's salutation (6) : SALAAM
20 Earnestly troubled losing last wandering sea-eagle (4) : ERNE

DOWN:
4 Raise for discussion south-eastern elk (5) : MOOSE
6 Concocted ale isn't a medicinal drink made from barley (6) : TISANE

Guidance as to finding the extra letters here would be appreciated. Many thanks in advance!

[JJ109]

1. It parses to Ma's alas. The S is not included, giving salaam
20 Earnestly - last = erney. The Y is not included, giving Erne

[JJ109]

6 anagram ale isnt = Tisane + L not included

[JJ109]

4 Moot (raise for discussion) + SE therefore the T is not included giving Moose

[Matakari]

Many thanks,JJ109, I’ve got a good idea now. Solving is done on two levels, the primary and then the parsing which can be tricky to determine the extra letter.

[ProfessorMaisie]

There appears to be a letter missing from the 4th word of the quote. Can it have something to do with the extra letters gimmick or is it a mistake? If it's the latter, it's a bad one (what do you think, Matakari).

[Matakari]

My apologies, ProfessorMaisie, I should have quoted the full preamble. Here it is: "An extra letter not entered in the grid is generated by wordplay in every clue; read in clue order the extra letters give instructions. Chambers Dictionary (2016) is recommended." I'll be seeking your expert guidance later, too! Thanks in advance!

[ProfessorMaisie]

It's the quote in the finished grid that appears to be deficient, Matakari - your initial question was fine.

When you finish the puzzle I think you'll see what I'm getting at (good luck).

[Neveracrossword]

Matakari, your seeking help prompted me to have a go at this puzzle. I've just finished it - mistake and all - and was left wondering, what was 'fascinating' about it? I kept worrying that I'd missed something significant!