Can 2 locality Khasra Number be possible?

Hi so we are looking to buy a builder Flat in new constructing building, so the Khasra 257, 0/102,No on the area of documents and address says of 2 locality and he showed us that the khasra has some portion in the Rajpur Khurd Extension and rest in Satbari Delhi (South), Builder said so we have to put both in the address. When i checked online i cant find 257 Khasra No in any of the above area in the options. But when i checked 258 Maps i could see Khasra No 257 in the map of Satbari in the exact location where we are buying flat. So why no Khasra no directly on top of the list ? Is it because it is landing in both localities?? Some of the people saying builder is doing it illegally as no registration happening in the area, wheres we saw recent Jan’s 2024 registry in that Khasra no 257 and checked e serach property can see registery details online with both localities mentioned on it.. can Sub Registrar confirm whether it is legal or not ? Builder also said check online or check directly through Sub registrar office ? Any suggestions what questions should i ask more to double sure before i invest ? Thank you your valuable suggestions much appreciated