Gaining a fourth Adventure Squad recruit from the Hunting Log

[Sonikku]

Hi, I'm new here.

I've reached 2nd Lt with the Adders and am told I need to find a fourth member to continue further and that they're unlocked through the hunting log. I'm currently working through the Battles category, but the last one, "Complete and mark off 3 Wondrous Tails" called "tales of derring-do bad and good luck" requires three tails.

And yet, near as I can tell you can only do one a week and the log progress resets weekly. So am I supposed to do 3 wondrous tails in one week to top off the category? Also, what are the odds of unlocking a squad recruit? It seems extremely low.