>>3485351The meter reads the exposure value. It doesn't set it to some number, it figures out what the ev is.
(assuming something like matrix metering, look up your metering modes and read about them)
It does this by taking the brightness levels from across the frame, then essentially adding them up, and figuring out what it has to divide/multiple them with to get an average brightness of middle gray. This is then related back to some table or pumped through a formula to spit out the exposure value.
The exposure value then is what's used to select the triangle settings like in pic related (red lines are ev's).