How can I print the special paper size (18 cm X 13 cm) format for SAPSPrint

Hi,

My printer is EPSON LQ-2180C(Dot matrix printer), and we had created sapscript form which is 18cm X 13cm,

it can print successfully, but its format is always A4 size,   any ideas for this ? how should I do to solve this problem ??

Thanks !!