This is one of those things in technical writing where you're damned if you do and you're damned if you don't. If they had said place control markers and troop pieces close by someone would have asked if they should remove all the control markers and troop pieces that the scenario says to place on the board. If they said place all remaining control markers and troop pieces close by someone will ask about what if there are none on the board. I've been in design meetings where language like this has resulted in a 20 minute verbal slug-fest to placate some engineer that thinks he needs to make a stand for some unknown reason.
When you consider that the "remaining" in the sentence likely modifies both the "control markers" and the "troop pieces" it becomes a fully correct use of the language. In the meantime it's worth asking if you're unsure that you're doing something correctly.