Hcg not exactly doubling 48hrs

Ryna

My hcg

7th July: 246

12th july: 838

Going for hcg again today on 15th july.

Is it 48hrs it doubles or cant it be anything between 48hrs to 72hrs?

I am little worried now.

Update: Good news my hcg increase by good numbers. Its not doubled exactly in 48hrs though.

15july: 1742