{% assign list = site.data.symbolon | sort:'number'%}
{% for s in list %}
{% assign image = '0' | append: s.number %}
{% comment %}
Using image|slice:-2,2 would be much easier here. However, it seems the
slice filer is not working for some time now…
{% endcomment %}
{% assign len = image | size %}
{% if len == 3 %}
{% assign image = '' | append: s.number %}
{% endif %}
{% endfor %}
{{s.number}}. {{s.name}}