Place the insertion point in a text frame to view counts for the entire thread of frames (the story), or select text to view counts only for the selected text.
Choose Window > Info to display the Info panel.
Your frames have to be threaded and overset text will appear as something like "Characters: 605070+11421" the plus being the overset.
If you don't have your frames threaded (linked) then you will have to insert your pointer to each one.
You can view threaded frames by View>Show Text Threads
When you click a text box it will show where it is threaded to.
But hey if you're really stuck you can do this
Export the File to PDF, overset text won't be exported.
Open the PDF
Save as RTF
Then open in Word.
This is one of the few times Word can come in handy!