About Using Selected Features
By default all features within a selected layer/data set are used in
the
conflation process. If features
from the layer are selected within the map, you may choose to eliminate
features NOT selected from the conflation process by using the Use
Only Selected Features option.
How to Use the Selected Features
"Use Only Selected Features" Checkbox 
To use only the selected features in the conflation process, click
the "Use Only Selected Features" checkbox
until a check appears in the box. If the box
is unchecked, all features within the selected layer or data set will
be used in the conflation.