The $300 educator expense is not added to your refund. It lowers the amount of income you are taxed on.
https://www.irs.gov/taxtopics/tc458
https://ttlc.intuit.com/turbotax-support/en-us/help-article/tax-credits-deductions/educator-expense-deduction/L4ez9qGKu_US_en_US?uid=m5zq4nk2