Wow so much feedback, forgot to check after I heard back from Groundspeak. If it is a micro or any container for that matter it should be labeled what it is not a question icon. I think you guys make a good point on just put a X on the spot so it leaves it open without any doubt. Here is what groundpeak wrote back.
Thank you for contacting us. No, you selected the correct size option. The "question" mark represents a "puzzle cache", which has additional waypoints and clues to get the player to the final location of the physical cache.
Please let me know if you have additional questions.
Best regards,