"Other" folder on SD card with Kindle Fire 10 A friend of mine has a new Kindle Fire 10 tablet and has a 64GB SD card.

When downloading content from Amazon Prime, the SD card fills up with more data than the content downloaded 

This content is stored in the "Other" folder but no idea what this

Does anyone know?
"Other" is cached data (browser, other apps), downloaded files, game data (e.g., Minecraft worlds), etc. Basically anything that doesn't fit the named categories.

You can clean some of this up by using the functions in Settings->Storage to clear app caches/data, delete downloads, etc. If you know what to look for, you can also use a file manager to manually delete things that may not get cleared via Settings menus. However, please make sure you know what you are deleting if you attempt the latter.