List Attributes Tags are used to output custom details about the List to the content. These tags are filled after a campaign is created, though can also be viewed in Template Preview by entering a Contact Email address and selecting a List. For more details, see List Attributes Tab.
List Attribute Tags in Content
List Attributes tags are built by adding the 'em_list_' in front of the List Attribute name to create the email list tag. For example, to pull an attribute named salesperson into a template, use the tag: %%$em_list_salesperson%%.
Only those attributes that contain a Value defined in the List Properties, Attributes tab will fill in your content. For example, you have defined three attributes in your Lists: version, frequency, source.
The tags for these attributes are: %%$em_list_version%%, %%$em_list_frequency%%, %%$em_list_source%%.
However, in your List, you have only set the value for frequency: Monthly. When you deploy your campaign, only the tag for %%$em_list_frequency%% will be defined.
*Feature introduced in v11.10.