how to specify this range for row security P4114 or P4112

Hi,  kindly advice how to specify the range - From Thru in the row security workbench in order to secure this field from being changed or removed...only can view

*blank to * blank does it mean only for blank value ?

FYI, location could have alphanumeric

Eg

F4111------------Location-----------*BLACNK----------*BLANK----------n---------n----------n------y------LOCN

F4111------------Location--------------000000-----------999999 ------------n----------n---------n-------y-----LOCN

F4111------------Location-------------<>NULL-----------<>NULL----------n----------n---------n--------y----LOCN

which one is applicable ? pls advice

tq