Dupe Matching Rule for Custom Field not allowing import of contact

dupe match rule is applied to custom field
then tried to import the contacts (import file is having values of the custom field).. but import not successfull.
it says duplicate records found .. but database not having those values.

steps :
1) create one custom field of type Integer / Radio
( Label / Value pairs are :
Label Value
9876 25
1234 50
2348 75 )
2) go to administer panel / Duplicate Match.
edit the rule. add created custom field as the rule (do not add any other field to the rule)
3) Now try to import the file
( the example content of the file :
Main ID Email First Name Last Name
9876 kaya@mn.net Kaya Adams
1234 maya@ex.org Maya Jamla
2348 chhaya@uy.com Chhaya Jigi
Note : Main ID is the label of the field )
4) last step of import gives message that no contacts imoprted.. found duplicate contacts. (check the database if such values exists in the database)