Diagnose "Memory" checks the assigned memory.
The appliance memory has to be 512 MB minimum.
In special cases (old virtual appliances), only 256 MB are assigned.
The Diagnose checks this and warns in case the required minimum memory is not enough.
The option "Show Details" is used to display further Information about installed memory, this is helpful if the installed memory has to be changed or upgraded in hardware appliances.
The Memory specifications depending on the configured and licensed appliance can be found in the following document: REDDOXX Virtual Appliance Variants