Rollback not working using rollback tag

My Changelog xml:

<databaseChangeLog xmlns=“


    xsi:schemaLocation=“” logicalFilePath=“2014_06_dml_WN.xml”>

<span class=“Apple-tab-span” nothing happens. But when I run the rollback using rollbackcount as 2 it works and both the entries are deleted from databasechangelog and from the table as well. Am I doing anything wrong while creating tag or while doing rollback tag. Please help me on this?