I think it means keep everything valid. If you can remove something without the story loosing the plot, do it.
But then you're to write why it's compressed too.. I wonder, I wonder.
If you can figure out what these people want, they are opening submissions again...and this is interesting...
"Individual pieces in your manuscript may have appeared in journals, both in print and online, as long as the entire collection itself is unpublished. Pays $50 per piece."...ah yes, loopholes are always good...