Lets say I've limited the number of saved recent documents in settings to display only the last six recent documents. On the left hand side the list is now full. From now on the "newest recent document" will replace the "oldest recent document". But, because I have "pinned" the top two documents, they won't be included in the cycle of "newest recent document" replaces "oldest recent document" and they will stay on the list until I unpin them. The same applies to the top two folders under Recent Places.