Strange numbered markings on the back of trays

[Xqueeze_me]

So I purchased these from an eBay seller. I wouldn't rule them out as fake since the packaging is 99% legit but the strange numbered markings on the back of the tray makes me wonder why it is so... Would anyone be able to let me know if these are marked samples or something, please?

Thanks in advance!

 

[erine1881]

i think it means it was a sample. none of my regular shadows have it. but i got the gulf stream sample at update, and when i popped out the insert, i have the same "24" sketched on the bottom.