"the 15 minute rule - As much food as it will eat in 15 minutes" what thats mean?

my frog eat without limit every 20 second till 15 minute n not stop eating , i using pincers take some morio worms n sway it infront of their face n they eat like never full believe me less then 15 minute my frog eat around 50 worms its wrong right ?????

or i must release some prey n let them hunting n waitting how many prey they got for 15 minute