How your macros are set
First your calories: your maintenance from the Mifflin-St Jeor formula (or Katch-McArdle if you know your body fat), moved up or down for your goal. Then the split: protein at 1 gram per pound of bodyweight (capped at 35% of calories so the number stays realistic), fat at 25% of calories, and carbs fill the rest. It's the same split Forged Axis starts its members on.
What macros are
Macros are the three nutrients that carry calories. Protein and carbs have 4 calories per gram, fat has 9. Protein builds and keeps muscle, carbs fuel your training, and fat keeps your hormones and health in check.
Do you have to hit them exactly?
No. Landing within about 10% most days is plenty. If you only focus on two numbers, make them calories and protein. Carbs and fat can trade places day to day without changing your results much.
Adjust from your results
Weigh yourself a few mornings a week and watch the weekly average. If it hasn't moved the way you want after 2 to 3 weeks, change your calories by 100 to 200 a day, mostly from carbs and fat, and keep protein where it is.