Turbotax: "Basic Military Pay subtraction:
Basic military pay subtraction is for military personnel stationed on extended active duty for more than 90 days. The maximum deduction is $15,000 of extended active duty pay and decreases by $1 for every $1 of active duty military income above $15,000."
tax.virginia.gov:
"Up to $15,000 of military basic pay received during the taxable year may be exempted from Virginia income tax. The subtraction is reduced when military pay exceeds $15,000 and is fully phased out when pay reaches $30,000 (i.e., for every dollar that military basic pay exceeds $15,000, the subtraction is reduced by one dollar). Military personnel must serve on active duty for 90 days or more, and can be stationed inside or outside of Virginia."
Reading this excerpt from military.com, it states "Resident Service members serving on active duty that earn less than $30,000 (base pay) can deduct up to $15,000 from their Virginia Income tax. For every $1 of income over $15,000, the maximum subtraction is reduced by $1. Service members must be on active duty for 90 days or more to be eligible".
In each case, you must serve on active duty for more than 90 days even though the Turbo Tax wording may seem confusing.