What is "Proficiency" that I get when I kill monsters by ships?

[GunApiwat]

I see that there is "Proficiency Increase" after I killed sea monsters by ships but I don't know what it is and how many I have. I'm pretty sure that it's not ship EXP.
If there is anyone know about it, please answer me. Thank you.

 

[Leba]

It is Ship EXP.