Why does a 1.36 GB folder take up 21.7 GB on disk?

I copied a folder called « Lingoes [Portable] (free) » from my PC to my portable SSD (Transcend ESD310S), and the copying process took way longer than I expected. After it finished, I checked the properties and saw this:

• Size: 1.36 GB (1,461,725,915 bytes)
• Size on disk: 21.7 GB (23,403,429,888 bytes)

https://preview.redd.it/022i8myjv5cf1.png?width=709&format=png&auto=webp&s=7da81de582c010b021a7652592bbbb38018974be

Is this normal, or could it be a problem with the SSD itself?

If it’s not a hardware issue, how can I reduce the storage usage? Is there a way to make it just 1.36 GB or at least something smaller than 21.7 GB? I don’t want to delete anything, just want to store it more efficiently if possible. Thanks!