Hcg at 4 weeks

I’m 4 +5 based off of last period and had my first blood test for hcg levels done today. Got my results back tonight and they’re 153. Going from my last period, those levels are in the range for 4-5 weeks. But the range chart I got from my doctor says that only puts me at 2-3 weeks? How else would they be calculating it?

Also does 153 seem low? I know the goal is to double every 48 hours or so, but I can’t get in for another blood test until January 3rd due to the holidays.