I found this nifty chart provided by medtronic (attached). I would bet that you have not gone into your bolus setting ans allowed for dual and square wave to be active.
A square wave bolus will give you a flat bolus of insulin over a long period of time. Such as 1.5 units spread evenly over 90 minutes. This function is a bit difficult to use by itself. I believe medtronic says it may be useful for grazing and/or high protein meals.
A dual wave bolus is a combination. First it provides a fast, normal (skittle) bolus. Second it is followed by a square wave bolus. Many people find this useful for high fat and/or high protein meals (like pizza). Many have noted that the high fat content in pizza slow down their digestion. As a consequence you may notice that you go low shortly after the meal (15-45 minutes?) and then spike later (3+ hours). You can use the dual wave to try to match your insulin's activity to your digestion. If done correctly (or luckily) you will not have the low or the late spike.
Setting up how much to do up front and how much to square wave seems to be very individual and will take some trial and error. Personally I like to put 15-25% of the bolus on the square wave and spread it out for 1 to 1.5 hours. The larger the square wave, then the longer time frame I will spread it out.
I would also invite you to reveiw the Total Available Glucose (TAG) group http://www.tudiabetes.org/group/tagers. As many of these issues are discussed more indepth there.
2218-DualSquareWaveQuickReferenceGuide1.pdf (1.88 MB)