The total $3700 is correct as shown on your W-2, Box 12, with Code W.
Employer contributions to a HSA are not considered income and are not subject to income tax or payroll tax. Since you, as the employee, also paid via a salary reduction arrangement, those contributions are also considered employer contributions. This means they're not subject to income tax or payroll tax.
Follow this link for a more detailed description: Employer vs. Employee HSA contributions.
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