Like the other sparkies said, the GFCI trips if there's a ground fault, which can be as low as something like only 5 milliamps. Its NOT an overload protection device which may require like 20 amps to trip. If the panel breaker is tripping there's either a problem with that breaker or a wiring issue somewhere in the branch circuit. Try a regular receptacle at that location and see if the breaker still trips?? Of course, the GFCI itself may be bad, but its hard to say from here just what the problem is.
John T Retired EE