2 sacs with one a lot smaller

I did IVF and they transfered 2 blasts. It looks like they both tried to implant because at my 7w2d ultrasound you can see 2 sacs. One is so much smaller than the other that my RE thought the smaller one would absorb. We did find one heartbeat in the bigger sac. I go in for another ultrasound on Monday to see if the 2nd one is aborbing or if a baby is in there. I was just curious if anyone had experiences like mine and ended up with twins.