In Storyline, there is a setting where you can specify if you'd like to launch your course in a new browser window (or a new browser tab on mobile devices). Per their article here, when you launch a course in a new browser window, you also get to decide how the new window behaves on desktop computers.
However, this will create an extra window when the course is launched in SCORM Cloud. For example, if your launch behavior is set to `New Window` than you'll see two windows when the course is launched.
To disable this, you have two options:
1. In Storyline, do not mark the box to Launch player in new window
2. Manually edit the imsmanifest.xml file in the course package and edit the following line:
<resource identifier="__672pQOiLmDF_course_id_RES" type="webcontent" adlcp:scormType="sco" href="launcher.html">
<resource identifier="__672pQOiLmDF_course_id_RES" type="webcontent" adlcp:scormType="sco" href="index_lms.html">
Then save the file, re-zip the package and re-import it.
If you have any questions, please contact us at firstname.lastname@example.org.