The tibia use the following to calculate the experience:
[(Base 100%) + all calculated bonus in %] * 1.5 stamina
To focus in your question I will calculate without stamina bonus.
Example: a monster give you 1000 experience points at 100%, if you are in party(ED+EK) its more 30%, so you have 1300 XP to share with your friend, that is, 650 for each.
During the event you will receive an additional 30%, so you will have 1600 XP to share, 800 for each.
In your example, you was doing 10kk/h without the event and without stamina boost with 100% (note here, that the % party does not appear on your skill's windows, so in fact this 10kk/h already refers to 130%), with the event you receive more 30% and got 13kk/h.
https://tibia.fandom.com/wiki/Experience_Point