Running concatenate on ORC tables either increase or decrease the number of files depends on the order of file being picked

I ran concatenate 2 times without changing any config

For the 1st run, 14 files merged to 8 files

For the 2nd run, 8 files expanded to 10 files

From logs i could see Input files are same, whereas output splits from CombineHiveInputFormat are varying depending upon the file being picked first.