[2/4] Right click and a quick "inspect" on the number, I found out the element's class name is "view_notification_random".
Awesome variable naming guys.
So you're _randomly_ trying to freak me out. Alright >>
[3/4] So what's your sophisticated pseudo-random algorithm?
Apparently, OneTravel are choosing a number between 28 and 45.
Because as you all know, based on serious psychological research, these numbers tend to make people book their flights fast #sarcasm #not42 >>
[4/4] Here's a bonus graph.
Thanks
@IddoYadlin and #WolframAlpha.