Without seeing your entire tax return, it is hard to know exactly what is going on. However, based on this W-2 your total income of $51,496 minus the standard deduction for a single person of $12,550 leaves you with a taxable income of $38,946. According to page 7 of the tax tables, the tax on that is $4,472.
You had $6,434 withheld and owed $4,472. That results in a refund of $1,962.
