There's an article explaining what a 'diffuse surface' (or material) means: https://en.wikipedia.org/wiki/Diffuse_reflection And the classic: http://www.huevaluechroma.com/021.php
in the maya UV toolkit there's a texel density tool (see image) https://knowledge.autodesk.com/support/maya/learn-explore/caas/CloudHelp/cloudhelp/2022/ENU/Maya-Modeling/files/GUID-73BF7546-3BF2-44F3-9192-15A024CEC173-htm.html
There might be some leeway. Mine looks like this: https://cdna.artstation.com/p/resume_files/attachments/000/012/670/original/Brian_Choi_Resume.pdf?1548964581