Yo Matt! simple answer is 6u wasn't enough for breakfast, and lunch was spot on!
(but you don't say what you were before breakfast?)
Sorry can't remember if you're still on fixed dosages or if you're carb counting and I:C ratio'd up? How many strawberries and slices of toast did you have? I very rarely eat yogurt so don't know how much carbs/sugar it has in it - I guess there was more carbs in there than your thought. And much less in your lunch?
The other factor is that your I:C ratio probably fluctuates a lot depending on the time of day/meal
Edit to add: Are you keeping a food diary as well as blood tests and dosages?