When we create substance materials for publishing purposes, we usually set the graph output mode to 'relative to parent', so that downstream users can dial the output resolution down if their system is slow.
However, the substance author sometimes has a preferred resolution in mind. For example, when working on a substance with a larger physical size, say, 20cm, the author may work in 4K, and would recommend using that resolution, when the harware permits, to take full advantage of the detail available in the texture. When the graph is set to 'relative to parent' though, no absolute default size can be entered in the Designer UI. It would also be helpful if the application where the sbsar is imported could set the output resoution to that recommended value by default after importing the sbsar. Or at least, hint the user about what the recommended size is.
When the inheritance method of the graph's Output size property is set to Relative to parent, you may change the parent size using the Parent size option in the graph toolbar.
Alternatively, you may change the property's inheritance method to Absolute, which we do not recommend as the resolution will be locked when the graph is published. You can learn more about best practices for publishing Substance 3D asset files (SBSAR) here.
You can learn more about the Ouptut size property and how it relates to the inheritance method in this page of our documentation.
You can use Comments or Frames in a graph to suggest a parent resolution to the user.
You may also add a text file to your package, which includes usage recommendations, and it will be included in the Substance 3D asset file (SBSAR) when published. The SBSAR file can then be unzipped by the user to retrieve the text file.