High HCG, but brown spotting?

[alwayscoffee]

I got my blood drawn at 4 weeks 0 days and it came back as 1,943. Which everyone is telling me that it's really good and high. Why am I having brown spotting then? I'm going to recheck my HCG levels on Monday to make sure they are doubling!

 

[Mystery26]

Could be implantation bleeding