Weird Measurements..Arg!

I have done well today and saved some cals back so I could splurge and have pasta tonight.  I sat down to figure out dinner cals and looked up Barilla penne pasta.  It says 200 cals for 1/8 of a box!  How in the world do I figure that??  I no longer have the box as I pour all my pasta, rice, etc into big plastic containers to save space in my pantry.   Short of actually measuring it out into individual servings straight from the box how would you have any idea what a serving is???

Anyone here use this brand of pasta?  If so how much did you estimate a serving to be?  3/4 cup or so (cooked) maybe? 

I have two types of pasta in my cabinet.  3/4 of a dry cup of Healthy Harvest whole wheat pasta is 210 calories.   3/4 of a cup of dry Rotilla pasta is 180 calories.  I'd guess the serving size to be 3/4 of a cup... seems to be the common factor...

Thank you.  Hated to ask such a silly question....