Hi @gunnark17854189 , As per you screenshot, the filtering condition in split activity is [email is not empty] AND [last name is not empty] AND [phone is empty]. Result is 6, and complement record is around 30K. This might be because those 30K records might failed to satisfy any one of your above filtering condition.
If you wants to display those records in your complement's transition arrow, right click the arrow > display the target list and configure the list with @email, @lastName and @phone. You can analyse why this records came in this complement.
Another way is, open query activity > add data > add @email, @lastName and @phone. Run the workflow. Right click the Split complement's arrow > display the target list. You can analyse why this records came in this complement.