Yes, that is a very high reading 2 and a half hours after eating, but that depends on what you were before you started eating. The higher you start, the higher you finish. Did you take a reading before you started? It will have been the muesli that did it, especially if you had milk with it.
That should tell you that that food (Which is high carb) is not a good choice. That is quite a high reading. Here is some info from the home page on levels.