Steps to replicate the issue:

• Use a browser on iOS (tested with Safari and Chrome) or Safari on MacOS
• Open any page from fr:Catégorie:Page utilisant des références ayant des précisions, e.g. Harold Acton.

What happens?:

• Notice that sub-ref numbers are displayed incorrectly in the reference list (e.g. 311.)

• The same issue occurs while editing in VisualEditor
• The issue doesn't occur if you add ?safemode=1 to the URL which leads me to the assumption that some local CSS is responsible.
• Removing https://fr.wikipedia.org/wiki/MediaWiki:Gadget-Mobile.css#L-95 appears to fix the issue

What should have happened instead?:

• Show sub-reference numbers as intended (e.g. 3.1)

Other information:

• No issue when using Firefox or Chrome on MacOS, also no issue when using browsers on Android or Linux
• The issue doesn't occur on German, Italian, Spanish and Polish Wikipedia which also supports the assumption that frwiki CSS is responsible