"+" or "-",
the clause gives an absolute line number within the screen record. Each 01 level represents a screen record. The AT phrase of the ACCEPT and DISPLAY statements specifies the positioning of the start of the screen record relative to the start of the display screen. If the AT phrase is not specified, then line 1 is the first line on the screen.
"+" or "-",
is specified in the LINE clause, then the line number is relative to that at which the preceding screen item ends, regardless of whether or not the statement displays the preceding item on the screen. This depends on the current effective length of that item at run time, derived from its PICTURE, VALUE and SIZE clauses. The counting of line numbers restarts at a level 01 item at line 1.
"+" or "-",
is specified in the LINE clause, and an ACCEPT or DISPLAY statement referencing the Screen Section item includes the AT LINE NUMBER phrase, the line number at which this item is presented is the sum or difference of the two numbers.