It is highly likely the piece you highlighted in the last image has the extra part you can’t see fallen to the build plate and obscured by the part you can.
Remove all the other parts.
Select the one of the two remaining parts from the object tab (far left), we are about to work out which one we need.
Using the top toolbar, select the MOVE tool.
The selected object should now have some arrows around it, use the UP arrow, this is a test only.
Move it up in the air, dies it look like the top part? If yes, remember which of the two objects it is.
Ideally double click the object name and call it top.
If it isn’t, double click the other object and call it top.
Select both objects and MERGE them.
Select the ‘top’ object, use the MOVE tool once more and slowly move it up. When you release this time it will stay where you left it. Now you can tweak the location with the z position box.
When you are comfortable, you can print the part.