Third Strike "Legally Caught"

[JPaco54]

Having trouble with understanding - "Legally Caught" as in reference to 6.05 B, "If a foul-tip first strikes the catcher’s glove and then goes on through and is caught by both hands against his body or protector, before the ball touches the ground, it is a strike, and if third strike, batter is out. If smothered against his body or protector, it is a catch provided the ball struck the catcher’s glove or hand first."

Not sure what it means, "...goes on through and is caught by both hands against his body or protector....."

I thought a foul tip was a direct stike to the catcher's glove and had to be caught. It seems the catcher can bobble the ball before it hits the ground.

If there is an old link to this subject please advise so we can allow for other discussions.