Whats wrong with my Ssd storage

According to the part number of the SSD (WDS500G3X0C-00SJG0) it is a 500GB Western Digital NVMe SSD which requires a special adapter to work in a Mac laptop. I think the seller is playing games with you and somehow was able to get macOS to show it as a 1TB drive. I would ask for my money back.

Here is the data sheet for that SSD (look at the bottom of page 2 for the part number):

https://documents.westerndigital.com/content/dam/doc-library/en_us/assets/public/western-digital/product/internal-drives/wd-black-ssd/product-brief-wd-black-sn750-nvme-ssd.pdf