AppleScript list FAQ: How do I get the AppleScript list size, i.e., the size of an AppleScript list (or number of items in a list)?
To get the count of the number of items in an AppleScript list, use this syntax:
set myList to {"Problem", "There was a problem", "Bummer"}
set listSize to count of myList
The variable listSize will now contain the AppleScript list size (the number of items in the AppleScript list named myList).