You have to keep in mind the following:
- 1 gram of fat yields 9 calories
- 1 gram of carbohydrate yields 4 calories
- 1 gram of protein yields 4 calories
so for the food you are eating:
Carbohydrates - 75g ==>75*4 = 300 cal
Proteins - 6g ==>6*4 = 24 cal
Fat - 15g ==>15*9 = 135 cal
==>Carb+protein+fat gives total calories = 300+24+135 = 459 cal
as for the vitamin/minerals:
Cholesterol - 0mg
Calcium - 60mg
Iron - 8mg
Those are not related to calories.
In general, nutrition labels should have a percentage daily value on the right side, which for these vitamins tells you how much percent of the required daily value that you need, does your food contain.
The vitamin/mineral daily requirements depend on your age and gender and is about how much (grams,mg,mcg.etc..) of each is required per day. You can check Health CANADA's website, they have a lot of info.