That RAM code means that it was a (2 x 4GB) kit; (2 x 4GB) means: two RAM sticks, 4GB each one.
Your screenshot says:
- Total capacity: 4GB
- Capacity for module: 4GB
- Memory features: ECC memory
- Number of modules: 2
By the way, the title says 4GB.
If I were you, I would have asked him how many modules there were.
The seller sold you one 4GB RAM stick as the title says.
It was part of a two sticks kit.
Also: it seems this RAM could not be compatibile with your motherboard and cpu, given that the ECC features is present in its description.
After searching it on Internet, it seems the RAM is NON -ECC.