You have run a Smart Campaign with a single flow step, Change Data Value, and you do not see the entire campaign membership in the Results Tab.
This can be expected. If the Flow step is changing an attribute to a given value ("example value"), but a lead record that qualified for the campaign already has "example value" in the field, there will be no change and the record will not display in the Results tab.
If the record already has the value, Marketo will not write another change on the activity log and so the record will not show in the Results Tab.
Is this article helpful ?