I just bought a new Thinkpad E495 with 16 GB (8x2) of RAM. I understand that some amount of memory is reserved for the system. Basing on other discussions I've read online, 2.4 GB is a very substantial amount to be reserved. On this machine, using multiple different distros, I only have access to 13.6 GB out of 16 GB.
Why can I access only 13.6 GB?
I can confirm the memory works because, using the Lenovo hardware diagnostic tool, all tests pass and it recognizes all the 16 GB.