Estimated print time

Hello gys, i’m new to Klipper but I love it already.
I was wondering if it’s common to get inaccurate print time from slicers to actual print.
I’ve an old i3 mega and noted that slicer report print time like 30 min and it actually take 40min-ish or even more … usual up to 30% more
I know this may vary due to multiple factor like acceleration etc and yet a friend of mine with a Fling bear 5 was doing some test on klipper too and he always get spot on estimated time … was odd to me :smiley:
we both use 3000 accel …
where can i look to see what could be the reason behind this inaccurate time? ( not a big issue … but i’m curious)
thanks :wink: