First, you need to know whether these are real styles or record of
formatting. If you have the Tools > Options> Edit setting 'keep track of
formatting' on, then Word will show you all variations from your styles.
This is very useful to spot deviations from style and to help clean up
documents, but can be confusing. Also, if you select one of these entries in
the Styles and Formatting task pane and click 'Modify' Word will convert it
into a real style with the same name (Normal + Arial or whatever) which
serves to muddy the water.
If it is formatting you are seeing, then you can change the option so you no
longer see it, or use the information to reapply styles as necessary.
If on changing the option you still see styles you don't want, then check in
the dropdown at the bottom of the Styles and Formatting task pane that you
have 'Available Styles' and not 'All Styles'.
If you still see styles you no longer use, you can either delete them using
the Styles and Formatting task pane, or hide their visibility by selecting
Custom in the pane dropdown and checking/unchecking names in the list.
