what is misc 2% itemized deduction (state only) on form 2106?

I work in the airline biz, and can deduct the differences between what we get paid while at work (away from home), and what the CONUS per diem rate. Turbotax is asking me to choose one of the 5 options, and 4 of them doesn't apply to me, and the last one says "misc 2% itemized deduction". What does that mean? The software seems to want me to pick one.