>> You can only call dibs on each item once.
Excellent. That prevents re-requesting a thing unintentionally. I agree that larger quantities can be requested offline.
Sometimes the seeds are precious and counted out by hand parsimoniously, and "extras" means 22 instead of 20.
Sometimes we have lots and a request turns into a tablespoonful.
Invariably (in other swaps), there is something I've been looking for, for ages, and I forget within a day or two that I clicked once. Invariably I will forget, then start to request it again, and sometimes my paper records will inform me I already asked for it, when I go to record the request.