HCG level?

I went to the ER because of a scare. The ultrasound tech was an idiot and didn't seem to know anything. (Worst first ultrasound ever!) but anyway, I thought I was 6w, found out I was about 5w4d. My question for you guys is, my HCG level was 4,681...what does that mean? And I only saw one sack but like I said, he wasn't the sharpest tool in the shed, is it possible to not catch a second sack on an ultrasound this early?? And are those normal numbers?