“Normal” serum hcg increase?

First, I know the normal range is vast, I’m just curious what other experiences were. Due to bleeding a few days ago, I had serum hcg measured 2.5 days apart. First measurement was 225, second was 844. I’m currently approximately 5 weeks, so the numbers aren’t alarming me. I thought I understood that “normal” hcg is expected to double in 48-72 hours. My tests were 64 hours apart, and my hcg nearly quadrupled. Aside from relieved that the bleeding hopefully doesn’t mean anything bad, it’s this rate of increase that has me curious. Has anyone else had this kind of increase at this time? How soon did the symptoms set in? Any symptoms I’ve had have been mild so far, but this rate has me nervous!