I'm pretty sure he is talking about 100 guests times 6 ounces of meat per each, divided by 16 ounces per pound to determine how many total pounds needed. You could use 6 oz. or 8 oz. depending on how big the sandwiches are.
Reverse flow homebuilt 250, Rebel 23, Jenn-Air built in grill island, 18" Weber. Red Thermapen at Christmas! And the proud new owner of a Weber Performer