Label4
Position Label4 so its top edge lines up with Label3, and so its left edge starts at an offset of 10 away from the right edge of the list part:
Edge
Attachment
Top
Attachment type: XmATTACHOPPOSITEWIDGET
Offset: 0
Attached parts: Label3
Bottom
Attachment type: XmATTACHNONE
Left
Attachment type: XmATTACHWIDGET
Offset: 10
Attached parts: Multiple Select List1
Right
Attachment type: XmATTACHNONE
Last modified date: 01/29/2015