Femara/letrozole starting CD6???

April

My RE prescribed letrozole when I went for a scan on my CD 6 when she didn’t see any changes in the follicles size. So since I was already on CD 6, she asked me to start the same day till CD 10 so that I don’t loose out on this cycle. But I have always seen posts of people taking either from CD 2 or CD3. Do you think starting this medication at CD6 is a little late/will it affect ovulation in any way? I have PCOS and currently on metformin too..