Pregnancy confusion dates

My friend says she went for a scan and she is 9 weeks pregnant does this mean she conceived around 7 weeks ago. She has slept with a few people and I tried to explain to her if the scan said she was 9+1 it means she conceived around 7+1 weeks ago. She has told me it's rubbish and it's 9 weeks ago she conceived . Am I right or could she be 9 weeks pregnant but also have conceived 9 weeks ago :/