Thank you for your answer.
I got the a closer inductacnce value when I increase the size of the radiation boundary. I read that the boundary should be at least 1/4 of the wavelength. The woorking frequency is 13.56 MHz , the wavelenght is 22m , which is 5m ,so I drew a box with 8m high, long and wide for the boundary.
I used lumped port with 50 ohm impedance