I am assuming you're looking at the Cat Nutritional Chart. Low carb foods, a must for diabetic cats, will be higher in fats. You indicate you're feeding your cat Purina Pro Plan DM. There's Pro Plan (commercial) and there's Purina DM (prescription diet). If you're feeding Pro Plan, only a few selections are low carbs and under 10%.
You don't need an expensive prescription diet food like Purina DM to feed your cat. Commercial foods like Fancy Feast Classics and some Friskies Pates, to name a few, are under 10% carbs and will save you money.
If weight is an issue for your cat, smaller, controlled feeding portions will help. I don't allow my cat to graze on food. If your cat is a grazer, a timed feeder can be helpful.