Variables not properly set for backup status? "%s days of backups left"

I have this setup in my user system.yaml:

```
languages:
supported:
- nl
- en
default_lang: nl
include_default_lang: true
include_default_lang_file_extension: true
translations: true
translations_fallback: true
session_store_active: true
http_accept_language: true
override_locale: false
pages_fallback_only: false
debug: false
```

And I see this "%s days of backups left" in my backups tab of the admin panel: