You are paying less than face value, so the gain at maturity lifts your yield above the current yield.
Current yield is 5.26%, which counts only the coupon and ignores any gain or loss at maturity.
The exact YTM here is 6.18%. The textbook approximation gives 6.15%, which is close but not exact, especially for long maturities and deep discounts or premiums.
Next stepCompare this yield against other bonds of similar credit quality and maturity before buying.