Starting with FAB 3000 Version 8 there are some new features in compare jobs. First if you're not familiar with performing Job comparison in FAB 3000 please view the following link which contains an example and movie tutorial, https://support.numericalinnovations.com/support/discussions/topics/14000006933
Error Size Detection Logic: When differences are found between PCB designs this setting will allow you to better allow you to better pinpoint differences and eliminate any false positives.
Use the Error Extents: This is the default option. Basically when a comparison difference is found, it will not be considered an error unless the extents exceed the defined Error Size in both width and height. The advantage of this option is to eliminate any false positives due to slivering (from mathematical rounding).
Use the Error Area: When a comparison difference is found, FAB 3000 will calculate the entire area of the difference. If that calculated area exceeds the area of the Error size (squared) it will be flagged as a compare error. Thus if a long sliver is detected it will be highlighted.
Search Area: Choose the entire extents of the design (Extents), or only use the area currently displayed on your screen (Display). This allows you to pinpoint the comparison to a specific area.
Check Visible Layers Only: When checked only the layers that are currently ON will be processed by compare jobs. This allows you to pinpoint the comparison to a specific layers.