Sounds reasonably large, but not abnormally so. How tall is he? Generally speaking, boxers grow in height until a year or so of age, and then fill out over the next year or two. But puppies, just like human children, grow at different rates. The kid who towers over his classmates at age 10 or 12 may reach full height by 15 and be overtaken by his slower-growing peers in later years. Well, same with dogs
The best guide to his final adult height and weight is that of close relatives such as parents and any siblings from previous litters.