Note: In general, the DCUI displays the approximate amount of memory that is available to ESXi.
This issue occurs when:
A significant amount of memory may be reserved by system's firmware and thus not available to ESXi.
For example, your system may have 64 GiB of memory installed, of which only 63.5 GiB is available to ESXi. The remaining memory is reserved by the machine's firmware. In this case DCUI displays 63.5 GiB Memory.
The DCUI truncates values to one decimal place instead of rounding.
For example, if your system has 4.0 TiB of installed memory, of which 3.999 TiB is available to ESXi, the DCUI displays 3.9 TiB Memory.