Script task generate multiple instances

Hi everyone,

This is my process model, and I'm trying to find the cause for above issue:

So the process starts with receiving the Excel file that user uploaded, then parse the file to get data into CDT type which looks like below:

Then I use another script task to index and get all the case Ids.

The problem is that when I run it in debug, the Parse File node generate multiple instances, however I check the output variable and the results are not duplicated. I didn't config the MNI either.