SSD lost size after erasing NTFS to HFS+
In my opinion you didn't buy a 1 TB SSD but a 1 TB + 24 GB SSHD (a hybrid drive similar to Apple's Fusion Drives). At least 46949230 blocks à 512 Bytes amount to ~24 GB.

I haven't been able to find a model though (except for an SSHD option with the same sizes in some Dell laptops).

If the HDD part isn't visible at all, it's probably incompatible with macOS' disk framework.