"Of course your majesty has realised that a long time ago, am I right?!" X'DD... I see what you did there! So there are two possibilities, either he's telling him that she holds way more importance & potential than what he thought in an indirect way, or, that he knows sumn important about her that made the king keep her hidden/away from gaining power & wisdom all this time lmao... for now the first option is more probable than the second because for all we know he didn't really care or know anything about her so far... but we could be wrong & he could have been watching her closely all this time, who knows after all he is an imperor! & In general imperors of such an age & experience aren't that foolish or blind to their surroundings...