Pic?

This is the size they're becoming ripe. I'm growing in containers, but it's a 10x4 box. I don't think space is an issue.

Mislabeled maybe? Grown from seed?

Are they striped when ripe? If not, I'd agree that they're probably mislabled or a stray seed.

A couple of my plants first tomatoes ripened small this year. It happed with both early girl and big boy. The next trusses, which are likely about to begin blushing, seem to be normal size. I have no idea what caused it, I'm just throwing it out there that perhaps it's possible there is some environmental or genetic thing going on, as opposed to mislabeling, although it's totally possible that it is in fact just mislabeling. Either way, I hope you get some tasty tomatoes out of it.