Whar is wrong with SSRS report margin setting?

I used Visual Studio 2013 to created SSRS reports and one of them I set left and right margin 0.4 in by the report property.

Once I deploy them to a testing report server and use asp.net web form to load/print reports. On my computer I can print the 0.4 margin report as expected but on some other computers the 0.4 in margin report out of boundary and check the printer preview's left/right margin is 0.5. What is wrong with the setting? How Do I the report to keep 0.4 in margin on any user's computer?

Thanks!