Spray bug?

Only in Garry’s Mod do I have this problem.
I keep trying to upload sprays (right size, parameters and formats) but when I go in-game to add them, it says ALL of my images/vtfs/whatevers are 4,096 mb, even though out-of-game they’re only like 50 kb. This is sort of an annoying problem, can anyone help me fix this?
The file I’m trying to use is a 54kb .vtf file, 128x128.

they don’t have to be 128x128. they can be 526x526. i duno about the file size thing, maybe make a less detailed one?

You’re not listening; ALL of my files are 4,096 MB in size (4.1 GB). Outside of Gmod, they are all 50 kb. I’m wondering WHY and how to FIX it :[.