Using measurements - I am still not right!

I have been having these ENORMOUS bowls of oatmeal (porridge) the last couple of months and just being so full.  But I use the measuring cup everytime so it never dawned on me that I had the wrong amount.  I noticed yesterday, I was using the 2 cup measurement and not the 1 cup!  I was eating a TROUGH of oatmeal!  So I thought I was having ~300 calorie breakfast and I was really having ~600!!!!  Geesh.