Weight loss is achieved by sustaining a caloric deficit (Kcal burned > Kcal consumed). How many total calories boxers should eat depends on the particular boxer’s height, weight, and body fat percentage. There are various calculators online to help one determine how many calories to eat. (If interested, search for TDEE calculators.) However, know that your body ultimately determines how much food it needs and everything else is just an estimate. This goes for how many calories you should supposedly intake and how many calories are supposedly in the food you eat. So, the best advice here is to listen to your body and not take these numbers too seriously. (They’re still serious, however.)
The extent of one’s caloric deficit has implications on training and body composition. Generally, the greater the deficit, the more one’s performance suffers when training and the more muscle one would lose rather than fat. However, some people find an aggressive deficit more sustainable, because it takes less time to lose weight, and it may yield better fat loss. It is up to the boxer and their historical tendencies to figure out the extent of their caloric deficit, and what’s best to meet their weight loss goals.