How much should I be feeding of each if I'm mixing dry & wet food?

Hello, I've been doing some reading, both on here and off and I'm still really confused...I have two URI foster cats in my care. One guy is 10.2 lbs and the other is 12.1 lbs. I've been giving them meals 3x/day. I do wet food in the morning after meds so they know something good is coming after the meds. I do some wet food at dinnertime to keep them from trying to disturb us during meals (one guy is very persistent) and I do a scoop of dry food just before bedtime to keep them from waking us for food.

The wet food they are on is a 6 oz can that I give them a 1/3 of a can each meal, so they get 2/3 of a 6 oz can per day, 4 ounces per day. The dry stuff, the 10 lb cat gets 1/4 cup and the 12 lb cat gets roughly a 1/3 cup (I use a 1/4 cup scoop and then add a little more to his). 

The back of the wet food says 2-3 cans for the 8-12 lb weight, so now I'm concerned that they aren't getting enough food. But with the dry stuff added in, I'm getting confused. The food they've been getting is Solid Gold Shrimp & Tuna Recipe: http://www.solidgoldpet.com/products/shrimp-tuna The site says there is 119/kcal per 6 ounce can. In calories, that's 119,000? And I read on another thread to feed 20-25 calories per body weight per day? I'm so confused... They both seem very hungry still and I'm just at a loss to know how much to give them. Could someone help explain please?

1000 calories = 1 kilocalorie = 1 Calorie

(Note the capitalization between small calorie and large Calorie (which is what we typically think of for food)).

1000 cal = 1 kcal = 1 Cal for the most part. It's a confusing distinction. So in your case of wet food, they get roughly 79 kcal/Calories from the wet food.

I've read that the labels on cat food are typically for an intact cat (which require more Calories), but I have no clue if that's actually true or rumor mill that started one day. 20-25 is a good start to estimate. So for your 10.2lb cat and going with 25, that would be roughly 255 Calories. For your 12.1lb cat, 302.5 Calories. What is true is that every cat will need different amounts. It depends on their activity levels, and metabolism to some degree. So this shouldn't be your 100% answer until you see for yourself how much they actually require (this may require actively weighing and possibly Vet input).

You also didn't list the dry food you give them, which will also play into the Calorie amount.

Thanks for that clarification! I didn't know there was a difference between calories and Calories. That is very easy to confuse. To note, I am feeding them Wellness brand cat food. Bag says there is 556 kcal/cup. So my 12lber should have max 302.5 kcal per day? If I give 1/4 cup, that's 139 kcals, leaving 163.5 kcals to be divided between the moist food. So they actually should be getting more than 1 whole 6 oz can per day! Woah. I was actually under feeding them! On instinct, I upped it from 2/3 a day to 1/2 can per meal, and I'm glad I did!

Now that they're off meds, I'm going to switch to dry food twice per day and moist food for dinner. Now I feel confident I can do the math better!