Formal expression: compli(?)mentary and supplementary

[Tamara]

Hi

Sorry for my, too tiresome for a Saturday morning, question, but I can’t wait till Monday morning :).

It should be regarded as complimentary and supplementary to any detailed such submission which the BCS may have made, be making, or be intending to make.
http://www.bcs.org/upload/pdf/biometrics190704.pdf (section 4.1)

This is a very formal text taken from the official site of the British Computer Society.

To be honest, I don't understand the sentence...

I first suspected complementary… but anyway, 'complementary and supplementary' just reminds me the school course of geometry.... angles... :)
As I understand, in real life both words are used as synonyms. Or not?

Could you give any comments on the above?
_________________
It’s impossible to learn swimming without entering the water…

[Alan]

Hi Tamara,

I think it's necessary to sort out the complements, the compliments and the supplements.

Complimentary means flattering or paying compliments that are remarks of admiration or respect. You pay someone a compliment.

The adjective is also used to indicate given for free as when someone can get you complimentary tickets for a show or concert, often given for the sake of publicity

A complement can be a complete entity as used in the phrase a full complement ie all the officers and crew of a ship. It can also be used as the thing or person completing the whole.

Complementary suggests adding on to what is already there as in complementary medicine like for example acupuncture together with diet and other factors keeping you in good health.

Supplement is an addition of some sort often used to describe an extra magazine sold with a newspaper. It could also be something added to your food to improve an aspect of its effectiveness

Supplementary also suggests added on /in addition to. In parliamentary debates for example members often ask one question and then add a supplementary question related to the first and added to it. In this sense it's not necessarily needed to make something complete as with 'complementary'

So we come to your quote:

[Tamara]

Thank you, Alan…

Aha... So (just to summarise all of that for myself), comple(!)mentary and supplementary in 'real life' have, in principle, almost the same meanings as they had in my school geometry :):
1) completing smth. to the some agreed 'whole' and 2) adding/supplying something extra.

Thanks a lot!
_________________
It’s impossible to learn swimming without entering the water…