Perhaps it points to size of the file to be submitted. As far as I understood, a file which is to be submitted, should have less than or equal to 1024 characters. (Note: A tilde "~
" symbol means approximately). So in your case, server where you're submitting your source code file, will not accept files having more than 1024 characters.
Therefore, before submission, check no. of characters in your source code, as:
~$ wc -c source_code.txt