Today is my second day on the diet. I forgot the Complete Start Cereal at home, but had the Triple Grain Crips so I substitued these. Will that have any effect for today?

I don't think you'll have any problems because of the substitution. Complete start is just around 30 more calories than Triple Grains so in the scheme of things it won't make a difference.
At least you went with a JC substitution rather than a bad choice somewhere else.
Good luck!

Just have the Complete Start in place of where you had planned to have the Triple Grain, and it should work out just fine.