Deleting via web library
I currently don't have Zotero downloaded on any machine and I'm trying to cut down on my storage plan. I've deleted quite a bit from my web library but it hasn't seemed to make an effect on my storage number. I've emptied my "trash" in the web library, too. I've thought about downloading it just to see if that works but I fear the possibility of all those deleted files coming back (it was a very detailed "hmm do I ever want this?" process I don't want to repeat!). Am I missing something?
Also it's worth reading through Storage FAQ to understand what counts (and what doesn't) for your quota.
If you're planning on removing many items (say more than a 100) I'd recommend using Zotero (desktop app) as it will offer better performance and it might be more efficient this way.