The golem number riddle (Puzzle room)

The players find a big stone golem with huge fists in a room. The golem then says:
"In order to proceed, you must solve the riddle. There once was a rogue, seeking to steal a priceless item from a powerful wizard. He sees a stone golem, much like this one, guarding a passageway. The thief sneaks away into a corner to think about what he should do. While he waits, he sees one of the wizard's followers approach the golem. The golem says 'Twelve', and the follower says 'Six'. The follower then proceeds through the passageway. Another follower comes. 'Six' the golem says. 'Three', responds the follower. The follower proceeds. The thief now knows what to do. The golem says to the thief 'Two'. The thief says 'one'. The thief is then smashed into the floor and killed. What should the thief have said?"
The theif thought the solution was half of the numbers that the golem was saying. The real solution was how many letters were in the number as it is written out. The thief should have responded 'Three'.