HCG levels and twins?

K

I am 15 DPO and had my HCG tested yesterday which came back at 1,663. I go back tomorrow for another test to check levels again. The doctor said this was normal in terms of my 4 weeks mark, but I have had others say it’s higher than some which has me wondering if I could be having twins? I go back toward the end of August for my next Ultrasound at about 7-8 weeks. What does everyone else think?