Does "I extended the list of phonetics symbols" sound natural in this context?

[Zoli]

I extended the list of phonetics symbols.

or should I say?

I added new symbols to the phonetic symbols list. (this repeats the word symbols twice)

Context:
I have a list of phonetic symbols and now I decided to append more symbols to the list.

 

[Tarheel]

The original is OK.

I might say:

I added some phonetic symbols to the list.

If you say something twice you have only repeated yourself once.

I assume those are symbols already in existence. Is that right?

 

[Zoli]

I assume those are symbols already in existence. Is that right?

Yes.

Does this work?

I added additional phonetic symbols to the list.

 

[emsr2d2]

Yes.

Does this work?

I added additional phonetic symbols to the list.

It's not entirely wrong but it's tautologous - using "added additional" is unnecessary.

 

[Tdol]

What symbols did you add?