Bug: XP Threshold Too HIgh?



Just wanted to ask about the xp threshold. When I try setting up an easy encounter for 4 3rd level characters the generator treats the max xp threshold as 500, when it should be 300 according to the DMG (75 per 3rd lvl). Is this an intentional difficulty up scaling or is it a bug?

Thanks for your time.

EDIT: Apologies, turns out I’ve misunderstood the text that says “The closest threshold that is lower than the adjusted XP value of the monsters determines the encounter’s difficulty.”