Question about Lenovo IdeaPad – S340-15IIL

There are 8Gb installed.

According to the description, 4GB onBoard and 4GB installed = 8GB Total

Are 8GB or 4GB installed?

I saw that the "total memory" is 8GB, but under "installed memory" it only says 4GB and on another website it says that only 4GB is included from the factory. I therefore thought that 8GB was the maximum possible, but not necessarily available. Is 8GB actually available in the laptop?