Iceberg/Reserve order:
An Iceberg order allows you to submit an order (generally a large volume order) while publicly disclosing only a portion of the submitted order.
A list of various order types:
http://www.interactivebrokers.com/en/p.php?f=orderTypes
Why would MagicalTux do that? Why not execute the order and disclosing the size of the order publicly? Why HIDE portion of the order??
I think when the order executes, then it becomes public, but the point is that a portion of the order is kept hidden up until it executes.
But I might be wrong.