By default, this is calculated when the screen template is published (transaction /TCTM/EWMITSTEMPGEN). This can be customised to control which row the selected field appears in.
Example
The row for selection number was automatically created with the value ‘1’ by the template generation in the screenshot below.
Assigning the display row for a parameter
Field SELNO shown on row 1 as configured
In the screenshot below, the row is changed to ‘5’, with the selection number reflecting this change following a screen refresh.