This depends on your settings for References.
Tools > Options > Editing > Context Tagging (R) Options
If you have "Find references incrementally (faster)" turned on,
then when you do a find reference operation, it will scan files until
it finds one with a reference, then stop. Otherwise, it will go through
all the files containing potential references, looking for all real
references, up to a limit defined by "def_cb_max_references".
It's important to understand that finding references is a form
of a search. It first uses the cross-reference to determine
which files contain a particular identifier, then it visits each use
of that identifier and uses the context tagging to prove or
disprove whether it is a valid reference to the symbol you
are searching for references to. This can cause some files
to be in the list that have no matches. If you are using the
incremental option, these files will stay in the list, otherwise
they will be weeded out.
Hope this answers your questions.
