The XML file size is of my export from my site is showing as 10239KB
10239KB is NOT 10GB, it's 10 MB. That's a substantial difference!
The file size is not the problem. Maybe it's even a problem that you set the size in php.ini to such a high value. Have you tried something like 64M or 100M or something?
When you open the file in a text editor, does it look like an XML-based file?