How does texture compression work?

Hello!
How does texture compression work?

We have 4096x4096 texture:
image

An other texture with 1024x1024 resolution
image

Why does compressed texture increase size in the first case?
Why does compressed texture decrease size in the second case?

Also we set less quality to above textures, but didn’t change their resolution. When we tried to compress it, we got the same compressed size as on the screenshots.

Texture compression is not to optimise for download size but for VRAM usage which you can see between the [ ] brackets on the right.

Using compressed textures will mean that you can have more textures loaded in memory compared to when using standard image types.

It’s also a lossy compression so it will be at a slightly worse quality.

If you think it’s beyond ‘slightly worse’, can you post an example please. Maybe it’s something we can tweak?