@javi-er - Not a problem at all, I hadn't convinced myself I was up to it yet and should've commented sooner. Looking good!
Regarding names, though, maybe 'percentage' should be 'value'? Since it's not always a percentage, it implies a constraint that doesn't exist, and could give the incorrect impression it'll append % automatically.
I ran across discussion of the use of 'eyebrow' in the cards component, suggesting 'title' or 'pretitle' instead: https://www.drupal.org/project/drupal_cms/issues/3497385#comment-15934581 ✨ Implement designs for Cards component within Olivero for XB Active
I've started roughing this out using card-grid and accordion as a pattern.
Added link to documentation for custom theme generation.