If you collect more than one gift of the same typd, they will stack in your gifts box, i.e.: 2 batches of 150 stew, but when you place this stack you only get 150!!! The rest is gone from your gift box and not in the restaurant anywhere!
You can work around it by only accepting one of any type at a time, then placing it in your restaurant before acceptin another, but this is still a significant bug that needs to be addressed.