Same thing happened to another person on this site too regarding chicks from TSC. Thought they were getting Barred Rock pullets, ended up with two crossbred pullets and a Barred Rock cockerel.
And those are a few different hens, I've been playing with the barring gene in my Easter Egger lines.
It's not a purebred Barred Rock. She's not extended black with barring. She's silver-based partridge with barring.
She'll look similar to these hens once grown.