Ikut date period 8w tp scan 6w

Salam nak tanya. Kalau kita ikut tarikh 1st day last period, sy da pregnant 8 minggu tapi tadi check doctor cakap size 6 minggu. So, kandungan saya nk kira 8 minggu or 6 minggu ya? Maaf tanya sbb 1st experience #1stbaby #ttc5years #endometrosisfighter #babypkp #baby2021