if u have onboard graphics that steals memory if your talking about RAM
and ever looked at the label
it says
"actual formatted capacity is less than advertised"
I think he is talking about non-volatile memory, such as SD, MMC and Compact Flash memory cards and USB Flash Drives...not volatile memory (RAM and CPU Cache etc...)...
...Besides with RAM, the entire capacity is allocated for system resources. You get the amount that is advertised. Whether the system allocates a portion of the system RAM to onboard graphics is none of their concern, because it's not needed for the RAM's operation.
However, with non-volatile memory such as USB flash drivers, SD and MMC memory cards, some of the storage capacity must be allocated for file structure information, in order for the storage device to be usable.