PlayStation 4 only 100 GB storage?

I bought a Playstation 4 on Ebay classifieds and downloaded games, but it says "Game can't be downloaded, insufficient storage space"

According to PS, I only have a total of 100GB of storage available.
Black Ops4 93GB and there are still 6.1GB on PS4.

But minimum storage capacity is 500GB, or am I wrong?

Maybe the seller installed a smaller plate?!

The previous owner will have grabbed the big hard drive and installed the small one. What was in the description regarding storage space?

I assumed that the PS has 500GB of memory and therefore I didn't ask. There was nothing in the description either.