Our crawler shows the following warning:
The item has been truncated in the index because it exceeds the maximum size. ( Item truncated. Field=docacl, Occurrences=3094, Chars=524453.
It concerns a SharePoint 2013 site-collection in 2010 mode. It refers to list items with unique permissions. Maximum of 10 groups per item. 400 items in the list itself.
When you google for this issue you will often find the following link: http://blog.mastykarz.nl/the-item-has-been-truncated-in-the-index-because-it-exceeds-the-maximum-size/
However, changing that property doesn't actually do anything unfortunately.