Posting exercise in my daily log

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Yesterday was my first day at Myfitnesspal.com. All went well with my postings, including the exercise. It told me I had extra calories I could consume.
Today, I have entered my breakfast and lunch and weight training that I did today. However, my log does not show any calories burned. Do we NOT burn calories with weight training? Yesterday, I had done 45 minutes of water aerobics and it showed I burned 306 calories. Why doesn't weight training show this?