No problem 10ss10. At 5' 8" women can have 4packs ... so one extra won't hurt you as a one off! If you find you want 4 meals - then split one of your packs and have 2smaller drinks. I have some clients who split a soup and have half at lunch time and have at dinner - and then do the same with a shake ... so they have dinner and pud!!
I'm the same height as you and my CDC said to me that if I was desperate for something(Especially in the first couple of weeks)to have an extra shake.
An extra shake is always better than the contents of a biscuit barrel I would think!