Heya. Sorry if someone already mentioned this - I did a search but didn't see it.
As far as I can tell, SDBs don't pay attention to how many uses are left in an object. It is really easy to mistakenly deposit new and used items together into the same SDB. This can be frustrating (like all the times I accidentally deposited my last empty firefly jar into my SDB full of 100 full ones) or even a bit misleading (like when I bought some of the new garden potions only to get home and realize that somewhere, somehow, I picked up some half empty ones.)
I'm not sure what the best solution is, though. My first inclination would be to suggest that SDBs don't allow you to mix new items and partially used items, but maybe they just need a better label? Or maybe they should automatically discount used items by a percentage, based on the number of uses left, kind of like how the AH does it? So, I might have an SDB for potions that sells at 1000c, but if you buy a bottle that's half gone, it only charges you 500c? Maybe I'm the only one who noticed it or overlooked an obvious indicator?
Maybe you should just let us make potions into gigantic barrels and people can come decant into their own containers, haha! ;)