If you are adding this list to exclude companies in a campaign, a better way is to do this:
Company Name IS
OR
Company Name STARTS WITH/CONTAINS
OR Inferred Name...
then place this smart list into your campaign by saying
Member of Smart List NOT IN "Excluded Companies List"
it is easier to make a positive set of statements, then to tell Marketo to NOT include that group, than it is to make a list of everyone who is NOT that.