So... analyze these two simple scripts here:
lighting = game:GetService("Lighting")
lighting.Blur.Size = 24 -- blur actually changes
lighting = game:GetService("Lighting")
blursize = lighting.Blur.Size
blursize = 24 -- blur does not change
Any idea why the former one works but the latter one doesn't? Thanks.

6 comments
The second code sets to what the value's number is, while the first is set up for the blur object itself.
@TheeDeathCaster How did you know :O?
@TheeDeathCaster can you clarify that a little bit? I am struggling to understand
So when you say: lighting.Blur.Size = 24, you are setting it's value; as opposed to when you say blurSize = lighting.Blur.Size, you are not making a shortcut to the blur's size, rather, your blurSize is just the number 24.
It's like saying
local y = 7 .... y = 28 <--Rewrites the variablefor the second code, while the first one changes the value itself instead of rewriting the variable. Think of the second code similar to this: http://wiki.roblox.com/index.php?title=Variable#SwappingI see. Thanks guys!