Overhauled carb leaking?

Just got my overhauled carb back, installed it and it leaks! First I turned on the electric fuel pump (it has no nose tank) and no leaks, then after it sat for a day, I tried it again and the fuel poured out!  I tapped on the carb with a rubber mallet and it stopped pouring out but dripped, I went away frustrated and called the repair shop, they said "run the engine and then check it" to me, an overhauled carb shouldn't leak, I don't see what running the engine is going to accomplished? Am I missing something here?