Did the breeder have Seramas for you to see? These are not Dutch chicks. Does the breeder raise Dutch, Old English Game Bantam--others? OR does the breeder cross breed the varieties? BAD THING. TO DO. Purchasing eggs is always a risk. Can be all cockerels, varieties mixed, without records of parent birds of EACH EGG, you will not be assured of decent representatives of any breed. Go on line, search for Serama sites and you may see chick pictures.
When the tails begin to grow, you will easily see Serama, if indeed they are Ss? Legs do not look short enough for good Seramas. However, you will have some lovely bantam pets, regardless of breed, so enjoy them, raise them well and maybe let us know what they look like in a couple of months. Good luck,,,,,,.