Page setup of RDLC report viewer

Question

When I print my report using thermal paper it's show 2 pages as you can see at the picture.

I already check my rdlc about the margin., But I think there is no problem with my margin because I set all size in 0 (zero).

Now, I try to open the Preferences / Page Setup and Edit

Now, after I click the edit I make a new paper config. I put a name Thermal_paper58mm.

Now here's the problem, I want to change the Width from 48.0mm the default to 58mm which is my thermal paper width, but I try to change to 49.0 or 50.0 else 58.0 nothing happened.

I want to ask somebody if they have a possible way to make a code to custom the Paper Config of RDLC Report Viewer using c# code.