"from a tool" Is this tool public? Can we see its documentation or download it somewhere? If not, it's going to be difficult to help you.
All we can say is that approximationResult is an object of class chebfun2 and that cols and rows are objects of class chebfun. They're all custom classes so the author may have customised the way they're displayed. And they must have or there's a major bug in there code since the size of the objects are reported negative. Negative sizes shouldn't be possible so I strongly suspect a bug somewhere in their code. The fact that the size reported is -9223372036854775808 which is the largest negative integer of type int64 is also a strong hint of a bug.
I'm afraid here, you'll have to contact the author of the tool to get them to fix their tool (and document it better probably).
