I may be missing something obvious here, but my food plan tile shows figures for calories in & calories out, but the difference of these figures doesn’t it doesn’t equal the calories left figure on the calories tile. Should these match, and if so, how do I get them to do so? If it helps, I do my food through myfitnesspal, but the exact calorie count syncs across.

They shouldn't match while the day is in progress, but will when the day is complete. On the fitbit dashboard the calories in/out and the food plan show two different things.

The calories in/out show whatever food was logged (or synched over) vs. your calorie burn so far. And your goal is applied (maintain, lose 1/2 pound, etc). When you understand how to use it, it can help you figure out how much activity you need to do if you are short of the energy balance that day. It can be hard to use to plan though since it isn't a full 24 hour calorie burn( (until it is).

The Food plan uses a 24 hour estimate of what you might burn. For time passed, it uses your actual Fitbit burn and for time remaining the estimate. How it estimates depends whether you chose "sedentary" or "personalized" in the fitbit food plan. (Personalized uses your recent average calorie burn as the estimate and sedentary assumes a sedentary activity level).

At the end of the day, they do converge because both will be your previous 24 hour calorie burn compared to logged food with your goal applied.