Visual Bug Experience

Hi, i'm a Mu player from Argentina, and i don't have the best English of the world, so i'll try my best with explaining my problem.
The server that i'm playing is a Season 9 with 60% exp
I have a bug that when i'm killing mobs of a high level, the experience bar and the numbers at the left (Obtained xxx Exp) are lower than mobs whose number of lvl is lower. But i know that this is visual, 'cause for example, if you kill a mob, and that mob gives you 1/8 of your bar, and you relog, you could have 5/8 of bar, or another bar. Other proof that this is visual is that you usually lvl up when you just have 6 bars, or 7.
I guess that the quanity of exp that i receive is the correct until the numbers should be higher than ~65000 and then it starts again to 0.
When you lvl up from a bar that is not 9, in the left corner there is a msg that says you get a lot of exp, for example, a mob usually gives you 45,000, and you get for ex. 1,965,540,450. I think that number is the remainder to the lvl up
I know you probably know about this bug, and there is a guide, but it's so old (7 years old), the pics are down.
If anyone could help me, he would be helping an entire server