AL, is that a trick question?.....;-). I will assume not. Since his 1.44 credit subtracted from his 31 Short Put ends up at 29.56....that is his BE. He can buy a 28 Long Put, for .30, which will prevent further loss below 28, but that reduces his credit to 1.14(1.44-.30), and he therefore raises his BE to 29.86. There is no way(I can think of) to lower his BE to "slightly above 28", in his current position.
Starting fresh, you can Short the Dec29Put and Long the Dec28Put for a .20 credit for a 28.80 BE. Options 101....less return for less risk and vice versa.
DATM; My question was about the UNDERLYING cause (factors) that would send the AGNC stock price down to $28 or below (aside from a momentary "flash" crash)? AND, what is the probability that a drop to $28 (or below) would occur? [If it's a very low %, then he need not concern himself with that protection --- buy insurance when you really need it and not waste $$$ on policies that don't provide very much protection.]