It's not a misspelling, it's simply an archaic form in use from the 1500's to about the 1800's. Latin form is completus, present participle of complere (to fill up) from com- "intesive prefix" +plere, "to fill," +plenus "full," +plethein "to be full."
Now place a damned order. Whatever it is, make sure you specify the colour.
BTW - they offer a wax formula which was reverse-engineered from a sample of Hasbro's new in house recipe... I think it's sold as "Azbro Mix." That's what I sculpt with.
... Haha, I said "plenus."