M0nica
You can also find out how much calcium there is in any food simply by googling 'How much calcium in .....' .
I dislike the ROS tables because they are far too vague. Giving how much calcium in an 'average' portion of cauliflower cheese is useless. How big is an 'average' portion. How much sauce is on the cauliflower, how much cheese does any individual put in their cheese sauce, what cheese do they use.
They talk about a bowl of porridge and give a weight. Is that of the porridge without bowl because bowls vary so much in weight from light plastic to heavy chunky pottery, the bowl alone could weigh more than th weight given for the porridge.
If you make it yourself, you can work out how much milk (or substitute) and/or cheese you've used. It doesn't have to be that exact anyway.
Once you've made it once, you can keep a record of how much calcium your serving size includes. That's what I've been doing for years, when I keep a record of carbs.