Hi there 
Please see Why does my game data increase, for no apparent reason?
This is due to the way that v10 Foundry handles database compaction with NeDB. Previous copies of documents are kept until a certain number of operations are performed, at which point the database gets compacted and size reduces again
Worlds are housed inside the Game/User Data folder so this will affect world sizes. I’d recommend making sure your world has a healthy buffer of about 30% of its own size or more in your Game/User Data folder if possible, but this isn’t a hard number by any means.
What might be more productive is to View Data Storage from The Forge and clear out any old or unused packages, or any zip files you find in the Others tab. You can sort by Size (Descending) to make it easier to see which packages are taking up the most space.
