Threat factor calculation for operable shutters

Hi, I was wondering how to calculate operable shutters that cover clear glass. Do I count this total area as a threat factor of 10 or do I add this on top of the threat factor area of 100 I am counting? As the shutters are usually open, exposing the clear glass, the area is generally a threat factor of 100, but when the shutters are occasionally closed, the threat factor diminishes to 10. I don't want to add the total facade area incorrectly but also don't want to incorrectly calculate the threat factor. Thank you!