The N40L comes with 1 × 2GB ECC RAM installed. It will accept up to 16GB (2 × 8GB) 240-Pin DDR3 SDRAM 1333 (PC3 10600) RAM  [Does this apply to all Gen7s?]
Non-ECC RAM is compatible, but not recommended for mission critical servers. Most casual, NAS or home server systems do not require ECC RAM.
Does not support registered (buffered) modules. Using registered modules will result in the server failing to POST/boot. (‘blue light’).
Capable of utilising dual channel RAM, which results in marginally increased memory speeds when two matched DIMMs are installed.
Ensure that RAM modules do not have large heat-sinks protruding from the top (clearance approx. 40mm from slot to chassis).