Nioh (a question about the mission map screen)

Anyone know what the deal is with the Red Swords displayed on each mission (directly below the recommended level) are supposed to indicate? There are between 1 & 5 of them displayed... do they reference the amount of deaths occurring in that level? The game as far as I can see has never explained it... and Google isn't helping.

Being in the 3rd area now I feel as though I should know how to read the game screen's information. So either it's a misstep on the devs side by not throwing up a quick note at some point to explain... or I'm blind and missed it.

Hi, I'm not 100 % sure, but i do believe it is the lengthof the mission, let say 1 blade is a enemy/boss like only, 2 it's a bit longer.... Hope that's clear

I always thought it was estimated mission difficulty. Maybe it has something to do with blood graves.