Changing Gmail settings

My Gmail account shows 50 conversations per page. I’m unable to change
this
setting to 25 through the gmailer-0.1.7 library. And this is three times
weird:

irb(main):004:0> require ‘gmailer’
=> true
irb(main):005:0> g= GMailer.connect(name,pwd)
irb(main):007:0> g.preference.max_page_size
=> “10”
irb(main):008:0> g.update_preference(:max_page_size=>964000)
=> true
irb(main):009:0> g.update_preference (:max_page_size=>25)
=> true

Is it just because I’m a Ruby monkey ?