Asset types are not translated from the Discovery Module.
The Discovery and Network Monitor modules do not share a common database for operating systems. There is mapping between the more common operating systems, like Windows and Linux, but there is no mapping for less common operating systems. Discovery will send Network Monitor a string with the full OS but it will enter it as the detail under the Description field instead of directly mapping to it.
You can manually adjust the Operating System and Asset Type of the assets by navigating to the Edit asset page buy clicking on the Edit link on the right hand side when clicking on the asset you want to change.
Kaseya 7 and up.