HCG too high?!

M
I shouldn't have googled because now I'm freaking out a little... 
My HCG at 4 weeks 4 days was 1630 with the reference range I found online being 5-426 for 4 weeks.
I had my second HCG at 5 weeks 3 days and it was 9,976 with the reference range being 18-7,340. I know for a fact that there's only one baby because I had an ultrasound at 5 weeks 3 days. Has anyone else had levels this high with one baby? I read high HCG can mean Down's syndrome..