Defensor corajoso

Within the first 5 seconds, I am scrolling to the bottom of the "rewards" list, and it shows "Defeat 10 Monsters 0/10" at 2 seconds in (I didn't realize it was there until someone pointed it out later, hence why I didn't really stop scrolling). At the 6 second mark, it shows I completed the "Defeat 10 Monsters" and gave me bronze medal, now asking me to defeat 100 monsters.