'Mem FromReport' - memory statgroup description

“Mem FromReport” exec command displays the mem stats, grouped into four categories:
STATGROUP_SceneMemory
STATGROUP_RHI
STATGROUP_Memory
STATGROUP_TextureGroup

Can anyone explain what the four categories actually stands for?

Addendum to above question, If we sum up leftmost link text elements their sum doesn’t match

Process Physical Memory

What should the sum match to?