You cannot change the width of individual pages within a list level. You can only change the width of all pages of a new list level. To do so, use the NEW-PAGE statement:
NEW-PAGE LINE-SIZE width.
All list levels starting from the new page have a width of width instead of the one specified in the REPORT statement. If you set width to 0, the system uses the width of the standard list (see Structure of the Standard List).
If you set width to sy-scols, you can adapt the width of the new list level to the window width, even if the window is smaller than the standard window. The sy-scols system field contains the number of characters of a line of the current window.
Within a list level, that is, if the next page is not the beginning of a new list level, the system ignores the LINE-SIZEoption.
For information on how to create new list levels, see Interactive Lists.