I believe it’s just a water splash mark.
Soundcore Motion Q - Wireless Stereo Pairing Review
Thought it was a crease myself, one of my Flare’s has a similar line…
“Creases”!
I got a lot, more than one! 
Nah, it actually looks like a cut to me not a crease. Kinda like when you open a box with a knife and it cuts into the product below
“The first cut is the deepest” 
Good review! I’m sure it will encourage others to get and enjoy this speaker 