If these debt securities are retired before maturity, the difference, if any, between the reacquisition price and the net carrying value of the extinguished debt should be recognized as a gain or loss by the fund that owned the securities.
There is a difference in retiring debt securities before maturity.
That's what I learned in Anthropology 101 from a professor who had to be at least 110, kept on the job by tenure and a network of Teflon tubing that functioned much like an actual large intestine.