Nancy, a single taxpayer paid $23,000 in medical expenses in 2018. Her AGI in 2018 was $50,000. Nancy filed a claim for reimbursement of medical expenses with her insurance company in 2018 but did not receive reimbursement until May 15, 2019. Nancy paid no other expenses in 2018. 

Assuming medical expenses have a 10% floor and the standard deduction in 2018 is $12,000, how much of the medical expense reimbursement must Nancy include in gross in 2019 if she receives a reimbursement of $23,000? Explain your answer?