HCG levels

Kelly

6wk today. Had blood test done 8/24 at 11am and got results the next day which read 717. Doctor said that was excellent and sent me for another blood test today. Just got results and she said "great news! Lab was 1214 so we can schedule an U/S for next week. I'm confused. How is this good? I thought HCG was supposed to double every 2-3 days? Over 5 days it didn't even double?? 😢