Fixed property values are the same wherever the resource is assigned. In the fixed property example values such as "manufacturer", "serial number", and "wavelength" are considered fixed because wherever the "spectrophotometer" resource is used those values remain the same. Fixed property values are a mechanism of automatic data entry for known values. When assigning a "spectrophotometer" the fixed properties of "manufacturer", "serial number", and "wavelength" would automatically be entered onto runs that resource is assigned to.
When using or changing fixed property values it is important to know that there is only one value used across all of Riffyn. If you change the fixed property value of a specific resource, then all instances where that resource is used will have their fixed property value updated.