QlikView seems to have some issues with large numbers, interpreting them as string only while loading. Not sure if this is what you see and if this is version specific, but if you are interested in, there are some threads that are related to problems with large number while loading from source.
I found some threads about problems with numbers, but usually they involved loading numbers from database, not calculating it. And seems in charts there are no problems with them, I assume they should work. But not, the problem is even when you calculate them.
Would be nice to heard a word from qt about why if I just multiply it by 1, it becomes a number again.