Form SC1040: Number of Days must be entered. I am putting 0 for subsistence allowance (multiply - days by $8), and it is not working. Keeps sending me back to fix it.

If you truly do not qualify for the deduction, then you need to make the space blank and then click the back button so the program thinks you were never there. By clicking continue, it is looking for an answer. 

Subsistence allowances of $8.00 per regular workday are allowed for police and all commissioned law enforcement officers who are paid by South Carolina municipal, county, or state governments or the federal government, and full-time firefighters and emergency medical service personnel.

Your employer should provide you with the number of workdays you are entitled to use for this deduction.