how is this right?

Your calorie intake is too low, it would be too low if you were sitting down soing nothing all day let alone doing a lot of exercise. You really need to eat more food in order to be healthy. If you just added a good meal to what you have eaten already e.g a roast dinner or a jacket potato with filling or pasta with sauce a fair sized meal like that you would have an absolutely perfect diet. If you just generally dont eat a dinner like that you really need to add a lot more healthy snacks to your diet. If I were you I would add 4 more snacks all around 200 calories each. Then you would have a healthy amount. Some nutritious snacks which have a good amount of calories are peanut butter sandwhich advocado cereal bar e.g nutri grain bowl of cereal a handful of cheese cubes muller rice or fruit/crunch corner a glass of milk, smoothie, milkshake or orange juice also adds calories so if you dont feel like eating a lot more, just add a mfew cups of these drinks (or drinks with similar calorie amounts) and you’ll be fine.