system
Given the following post, respond as if you're commenting on Reddit:
human
[Star Trek] What does it mean that "Shields are at 22%" when the opponent is already blowing actual holes in the Enterprise? Aren't shields doing nothing at that point?

As seen in multiple TNG episodes, movies, etc.

EDIT: I appreciate the responses so far, but I don't think anyone's adequately addressed the scenario where the ship is ACTUALLY BEING SHOT UP. Even if the shields are deflecting a certain percentage of the weapons' energy in some way, it's all for naught if the hull is being breached. "Shields useless" would be a better and more appropriate thing to say in that instance than "Shields at X percent."

(As a side note, I assume that the bridge and warp nacelles are protected by sterner stuff, since otherwise the enemy would immediately blow them up.)
gpt
Federation shields diffuse the energy from attacks.  As they get more and more attacks, their ability to diffuse the energy falls.  In your example, they are only able to eliminate 22% of the energy that's hitting them leaving 78% of the energy remaining to "blow actual holes" in the ship.