fetal fraction for harmony test?

Monica🌸
I had the ClariTest/Harmony test last week and just got my results. It said it was negative for the chromosomal abnormalities and that a Y chromosome was detected. I know that means that one or both of the twins are boys! 
My concern was that it mentioned that my fetal fraction was only 2% at 12 weeks? 
Anyone have this test done with multiples and results were low like this? Did it have any effect on your pregnancy? So far they're measuring perfectly and everything looks great. After 3 miscarriages, this is the furthest we've ever been and I'm stressing.😬