What is the use of the POSITION and SIZE command in SAP Scripts?

The POSITION command is used to x, y coordinate position which is used by the BOX command. The offset from the current window positions are specified which could be either positive or negative.
/: POSITION XORIGIN YORIGIN WINDOW PAGE

Eg.:
/: POSITION XORIGIN '2' CM YORIGIN '-1.5' CM

Similarly the SIZE command sets the width and height parameters.
/: SIZE WIDTH HEIGHT WINDOW PAGE

Eg.:
/: SIZE WIDTH 10 TW HEIGHT 10 TW