in reply to
after waiting for long here i decided to file a bug to the author of this module
this is what i got in response
I haven't put my hands in Gmail::Checker since 2004, and unfortunately
+, upgrades to the Gmail servers might affect the functioning of some
+of the functions.
The output of the number of emails is an output of the STAT command on
+ the POP server, as described in RFC 1939.
Thus this is the reply provided by the POP3 server. I will look into i
+t on my end in order to identify why the number of emails returned by
+ the server is wrong.
will post here if get something from his end