I have tried to find out what is the differences between Melins 380.x and 382 firmware? Is it depending om the router? Or are there an general explanation?
Basically, 382.xx is what comes after 380.xx, Asus simply bumped the version number because of the numerous changes. If you look at the changelog for Asus's 382_18881 recently released for the RT-AC68U, it will give you a hint as to what was changed since 380_7743, the previous 380 release for that model.
A lot of the changes are under the hood however, like better protection against buffer overrun through nvram values, the new Trend Micro engine, etc...