how to set name of folder to string in middle of original file name

I have a script that works great as shown below, but if I change line 13 from..

Open this Scriplet in your Editor:

set name of first_item to (text 1 thru 8 of theFile)

to

Open this Scriplet in your Editor:

set name of first_item to (text 2 thru 8 of theFile)

the script breaks.

Can someone please tell me why and/or how I can solve this?

Open this Scriplet in your Editor:

property dialog_timeout : 120 -- set the amount of time before dialogs auto-answer.

on adding folder items to this_folder after receiving dropped_items -- this_folder is an alias

  delay 5

  tell application "Finder"

    set this_folder_list to every folder of this_folder

    set this_file_list to every file of this_folder

    repeat with i in this_folder_list

      set first_item to item 1 of dropped_items -- name of entire path

      set theFile to (name of first_item)

      if kind of first_item is "folder" then

        set name of first_item to (text 1 thru 8 of theFile)

      end if

    end repeat

    set oldFiles to (every file of this_folder whose name starts with theFile)

    delete oldFiles

    delay 5

    repeat with i in this_folder_list

      set this_file_list to every file of i

      repeat with x in this_file_list

        set theFile to (name of x)

        set theFolderName to name of container of x

        set name of x to theFolderName & "_" & theFile

      end repeat

      set this_file_list_with_new_name to every file of i

      move this_file_list_with_new_name to this_folder

      delete i

      delay 5

      set unneededFiles to (every file of this_folder whose name extension is not in {"csv", "xml"})

      delete unneededFiles

    end repeat

  end tell

end adding folder items to