Dear Doctor, I Did A Routine Abdominal Obstrictics At Around

Dear Doctor,
I did a routine abdominal obstrictics at around 10 week 4th day (i.e. roughly middle of 11th week). In the result it is said that CRL is around 40.8 mm, which corresponds to a age of 10 week 5 days.
In the result it is also written as:
"Developing placenta seen posterior, lower magins
reaching upto the internal Os-for followup"
I just want to know whether it is normal (my doctor said normal, but very busy and did not say any details)? Please clearly explain me about the placenta stuff!! What are the chances of normal birth? are there any schematic picture to understand the location of the placenta with respect to the baby? or at least please mention in words about it.
Thanks,
COuples