Your employer added a contribution in the current tax year for the previous tax year. This happens sometimes.
Ordinarily, had the employer made the contribution in the previous tax year, then it would have been included with the Code W amount in box 12 on the W-2.
In your case, go through the HSA interview until you come to the screen entitled "Did your employer tell you about any other contributions?" (see screenshot).
Answer "yes" to expose the three bottom lines. You want to enter the $750 in the second line - "Employer and payroll contributions made in[ the current tax year] for [the previous tax year]"
P.S. enter the W-2 as is, with the $1,000 with code W in box 12.
[Edited 3/17/2020 5:10 pm CDT - made year neutral]
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