I know this has been brought up before (here or test I can't remember) but any exp gained inside an adventure/scenario by completing the quests does not actually add to your experience totals. For example:
This is taken right at the end of a Storm Recovery scenario. Note my total XP at 688,528,744. Now the dialogue box says that my reward for completing this step is 15,000 xp and that I have not clicked the green checkmark to receive it yet. Next:
This is after completion, but before accepting my loot mail. At this point I should have received the 15K xp but not the xp from the loot mail, however as you can see, my total xp remains unchanged at 688,528,744. This means the 15K I was supposed to receive did not add.
I have tested this on all the other steps and on other adv as well and it never adds the xp you get during advs. This can add up to a lot, especially with some side quests like on MCC where it costs a lot of resources and you are supposed to be getting 25K+ each time.