Form 568

Form 568 Schedule B Line 17a has defaulted a 0 in this field.  When I run error check it indicates that this field should be left blank for none, an entry of 0 is not allowed, but it will not let me remove the 0 in this field.  I never entered a 0 in this field.  Thanks for any help.  It will not let me complete my filing until this has been corrected.