None means that no permissions are assigned--neither allowed nor denied. So, if the user is part of another group, then those permissions will take precedence. Denied is always denied--it trumps any allows in other groups. Also, here's a good discussion for more details: Different "Deny" and "None" or "Unspecified" in permission
Still not very clear.
Okay, can you clarify your confusion then?
Remove permissions that will cause ambiguities
Every site has a Default project and an All Users group. The Default project works as a template for new projects in the site. Creating groups and setting baseline permissions here helps you to know and manage exactly who gets what level of access for each new project..
When we remove all content permission like project, workbook and datasource with none we are not giving any permission here with user.it will ask you to delete.
If you given denied or viewer etc then it will ask to save.
it may be clear in your doubt.