HCG number won't indicate twins - only your scan will confirm for sure.

I got BFP's at 9dpo with both my pregnancies - my HCG was tested at 16dpo, with the first one being 305 which was my DD and then the second my HCG was 351 and was the twins.

Congrats on your BFP but don't worry about how many you are carrying until your scan time, enjoy that you have a magical BFP