Most of us base our dose on the amount of carbs we want to eat, not a fixed amount of insulin per meal.
For instance, today's meal today needed only a single unit (cauliflower, minced meat, lots of cheese and some other very low carb stuff), but on other days I might need 15 units or more for a meal because I eat fish fingers or chips or such.
Have you looked into something like a DAFNE course to learn to adjust the amount of insulin to your carbs, or spoken with your consultant/DSN to see if they can help you find out your insulin to carbs ratio?
None of us can tell you how much insulin you would need for a particular meal. Some of us would need only 2 units, others would need 30 units, there is no way we can safely predict how much YOU need.