What does +zero do?

[Strykar]

I am trying to use the 0 (in Kitty terminal) with a . in it not the /. Setting +zero or -zero does not do it, and looking at https://github.com/tonsky/FiraCode/wiki/How-to-enable-stylistic-sets +cv15 does not either.
What am I missing here? What does +zero do exactly?
I wish all these alternate styles were documented better.

[wopian]

cv15 is for * positions/style, not 0

zero is 0 with a dot
cv11 is 0 with nothing inside
cv12 is 0 with a \ inside
cv13 is 0 with a | inside

[Strykar]

My kitty config has font_features FiraCode-Regular +ss01 +ss02 +ss03 +ss04 +ss05 +ss07 +ss08 +zero +onum +calt but the 0 is displayed as:

Shouldn't +zero set that to a zero with a dot?

[wopian]

Do you have an older version of Fira Code installed on your system from before stylistic sets were added in v2+?

[tonsky]

This is not Fira Code at all. Check your installation, maybe font name

[alexeyten]

Looks like Noto Sans Mono

[Strykar]

I am an idiot and had font_family FiraCode Regular instead of Fira Code Regular.
Looks good now, sorry for the wild goose chase.

I have one Q, what is the logic behind onum, is it just to fit more numbers in the same space?
I have a large 2K monitor and I realized I prefer the standard perfectly aligned way.

[tonsky]

onum enables “old-style numerals”. I believe the idea was that they start to behave like lower-case letters: some descend beyond baseline. Some might argue they look better in a text context. I personally never liked them all that much

[Strykar]

@tonsky Would you please reply in a new box so I can mark it as the answer. Thank you!

[tonsky]

This is not Fira Code at all. Check your installation, maybe font name