relevant info you might find useful (copypasted from what I told a DM in one of my campaigns who was confused about how it worked):
"this link does a good job of summing up how encounter XP works (though it doesn't elaborate on how "adjusted XP" works): https://rpg.stackexchange.com/a/70829/33569
As for that part, the adjusted XP (i.e. base encounter XP * modifiers) is basically for determining the difficulty of an encounter (based on whether one side outnumbers the other): https://www.sageadvice.eu/2016/03/26/adjusted-experience-points/