net-4.6.2: Microsoft .NET Framework 4.6.2
net-4.6: Microsoft .NET Framework 4.6
net-4.5.2: Microsoft .NET Framework 4.5.2
The page .NET Framework Versions and Dependencies.aspx) - covers the difference between various versions extensively.
In the future, the plan is to let developers specify which exact version of the .NET Framework their game targets, and to let the itch app determine if the player already has a sufficient version installed, or if a newer version if needed.
See the global Prerequisites documentation to learn how to add prerequisites to your game and what to do if the prerequisites or version you need isn't listed.