with my first they gave me the results based purely on my scan and it was something like 1:40000 and then threw my blood numbers in and it suddenly freaked me out because it went down to 1:750 - I wanted to know what caused the variation etc but no one could tell me other than 1:750 was still considered low risk - he was fine.
my third I had 1:199 - again he is fine. This time even though I'm older and starting further down the scale they went up to 1:1019 - still no guarantee but better than 2 out of the other 3.

Really 1:700 is a good number and the Edwards Disease number is good as well. I'm sure if there was one particular thing that worried them say your PAPP they would have told you. OP is right - with things like this (and most things medical) Google is not your friend. Its one of those things were only the bad things make the reports etc not the normal or average or good.

Try not to panic.