Twelveteen

This morning Eli was opening his present book from the advent basket. Here was the following conversation:

E: What number am I looking for Mom?
M: Eighteen.
E: (Flipping past a few 20something books) Ok, eighteen coming up!
E: (He got to 22 right before 18 and I could hear him under his breath say) Twelveteen, no.... I found it!