88 pounds is not average for a male shepherd, it's actually the top of the breed standard, which goes from approximately 66 pounds to approximately 88 pounds (30-40 kgs). I don't know how you'd even calculate an average size or weight.
That being said, many shepherds are larger than the breed standard, and a dog with a bigger frame can weigh more and still be an appropriate weight for his size, which is already several inches taller than the standard.
Most of the time when people ask if their dog is overweight or underweight (both of which are VERY common questions here) what they really seem to be asking is if their dog is big or small, which is not the same thing. A smaller dog can be overweight and a larger dog can be underweight. If he's a good weight, there should be a discernible "waist" when looking down on him from above and a tuck up at the abdomen when viewed from the side. When you run your hand down his side, you should easily feel his ribs but they should not protrude. Without photos showing those angles, it's impossible for us to tell.