I am going to be making the Basic White Sugar Shortbread recipe from the Argo Cornstarch site and have never seen this type of instruction -"Bake at 300F for 25-30 minutes". It is in all their shortbread recipes (of which there are many). This recipe is for 1 inch balls of dough.

http://www.argostarch.com/recipe_details.asp?id=1261 [1] 

Why wouldn't I just bake as I usually do for small cookies-350F for 8-10 minutes?