Not sure if you can change it, but this article talks to how training materials are marked complete.

https://help.docebo.com/hc/en-us/articles/360020126739-Marking-training-material-as-complete

----------------excerpt from article about videos------------------------------------------

Videos

Video training materials are marked as completed for learners using the following criteria:

• When the video reaches 15 seconds before the end marker if the video is longer than 150 seconds.
• When the video reaches 90% of completion from the start marker if the video is shorter than 150 seconds.

@JGildea as we didn't find a way to change it, at the end of each video, we are adding an 8-second long filler slide, with a message like “lesson completed”, “please proceed to the next lesson”, or ”thank you".

In that way, the module competion popup comes exactly at the end of the actual content.

Hey! You can hide it with CSS, by copy and pasting the code below in the Custom Styles area of the Branding Look and Feel.

However be aware that this will hide it from every course, not just the one with a video at the end.
 

/*Hide course completed pop up */
.dcb-course-lesson-player-idle-message { display: none !important; }