You did nothing wrong, its a matter of interpretation. What you are expecting if you put a request of 30 plates the bots bring 30 plates, thats not how the logistic network works. What you told the logistic network is that want to have a minimum of 30 plates in your inventory, because you already have 428 plates the bots wont do anything as your request is already filled. In short, from the game perspective you are a moving requester / active provider chest.
Guys, I have a new problem. I got a copy of blueprint found on factorioblueprints.com
When I use it, it doesn't fill enough items, only some of them, see the pictures:
As 0.12.32 broke old blueprint, in last version of blueprint string there is a update button, take you blueprint, and click on the button with it. Should work.
Want more space restriction ? Or maybe you want to be forced to use train for other thing than ore and oil ? Try Building Platform Mod !