For more, see Layer Management, Build MUID
An MUID is a MapSyc Unique Identification. GeoSync requires that a layer have an MUID when editing that layer or its Annotation.
With the Auto Increment MUID box checked, GeoSync assigns new MUIDs to features being appended from the source layer.
To add an MUID field:
See Modify DBF Structure.
The MUID Field Data Type is Long Integer.