So, I'm level 67 and drank the 300.-600% XP pot that GF gives us when a char reaches 65.
Started doing dungeons.
Had 15 billion XP when I started, after 2 runs I am down to 12 billion.
What is this? Is this how Gameforge expects us to reach 68 for the patch? How can I level if I LOSE XP if I do content? 
its the bug they havent fixed apparently
if a single kill gives you over 2.1 billion exp, whatever exceeds it overflows(because BHS cant be arsed ot properly code their integers) giving you a negative value instead.
the upcomnig pathc is supposed ot fix this but until then you need ot be wary whne using those pots on some content
Hi Keoland,
like Teixas already said, there is currently a bug which gives you 0 XP or negativ XP if you reach around 2 Billion XP with one Monster/Boss. This will be fixed in the upcoming Patch 86 next week.
no, it's because experience gained is a signed 32 bit integer, meaning it can take on values from -2^31 to 2^31-1, which turns out to be 2147483647. add one to that and you wrap back around to -2147483648 due to the way negative numbers are represented (two's complement). So it's quite literally impossible for you to gain 5b exp in one go.
it's unfortunate, of course, but has always been like this and will be fixed next week as stated.
EDIT: TC grants you more exp gained, so you might not have overcapped last time without TC.
Well, dang.
Must have been because of the TC GF offered when a char reaches 65, because last double XP event I did the same dungeons with the same potion with the same character and was getting about 5 billion XP a run with no issues...
seems likely
if you have TC, youll earn double exp permantely from all sources, using the potion on top of it might have put you over the cap
i dont have TC and after farming caiman portal for 2 hours i can confirm that 300% potion doesnt work at all, 50% and 100% works, lets see if its getting fixed in this patch
How do exactly plan to fix it without switching to 64 bit ? I mean, Tera runs as a 32 bit program, how they gonna fix something that exceeds how much a 32 integer can handle?
750M XP worth in potions in all dungeon 
How do exactly plan to fix it without switching to 64 bit ? I mean, Tera runs as a 32 bit program, how they gonna fix something that exceeds how much a 32 integer can handle?
They change the string from xp to 64
How do exactly plan to fix it without switching to 64 bit ? I mean, Tera runs as a 32 bit program, how they gonna fix something that exceeds how much a 32 integer can handle?
The same way 32 bit arithmetic was handled on old 16 bit machines. You take 2 32 bit adresses to store a 64 bit value. It's possible and very much standard in a lot of programming languages.
After all, boss hp has long exceeded 2 bil (or 4 if you consider uint32) and yet here we are.
How do exactly plan to fix it without switching to 64 bit ? I mean, Tera runs as a 32 bit program, how they gonna fix something that exceeds how much a 32 integer can handle?
You don't have to switch to 64bit to fix it. One way is to make it give you the xp 3 consecutive times for example so it doesn't exceed the 2.1b cap.
First step would be to change int32 to uint32 (unsigned, so the first bit does not count as + / - - so the max exp for once would be 2^32, not 2^32-1, which is about 4.2billion. This should solve it for a while. The other possibilities where mentioned
(just talking tech since im no the first one in the thread)
How do exactly plan to fix it without switching to 64 bit ? I mean, Tera runs as a 32 bit program, how they gonna fix something that exceeds how much a 32 integer can handle?
same way you did back in the 16 bit programming days
you split it into 2 values
this llows you the same range as a 64 bit integer, but it takes twice as long to call it
other way of getting aronud htis would include:
Splitting the exp of problematic mobs inot multiple instances
shifting to uints so your range increases ot 2^32(4.2 billion)
and mind you they have had ot done this before, since this was also a issue with boss HP, and they fixed it.
Just to clarify, they managed to fix this.
Sadly I didn't look at the exact numbers, but I got something like 15 billion exp from one portal with 2 golden larvae earlier.
