The stencil data may either be placed relative to the center of the frame or the frame edge.
If there is solder paste data for both sides of the board, then you may choose to include openings for both sides of the board on the same stencil by marking the Place top and bottom data on one stencil check box. You may also choose to add text indicating which set of openings applies to which side of the PCB.
If you do not choose to place top and bottom data on one stencil, then two stencil products will be created when you publish. When creating two stencils, you may choose either to place the data at the same location on each stencil, or specify individual locations for the top and bottom data. If individual locations are chosen, then you may choose to separate the two sides either horizontally or vertically. Use the Swap left/right data position check box to swap the positions of the two layers.
If the data is placed relative to the center of the frame, then an offset may be specified. You may also choose between anchoring the data either to the center of the board outline or the center of the solder paste openings. If top and bottom data is specified with individual locations, then you should specify the distance between the two boards.
If the data is placed relative to the frame edge, then you must specify offsets. You may choose either to specify offset from the frame edge to the farthest board edge or from the frame edge to the nearest board edge. (If there is data for both sides of the board, then there will be two offsets, one from each edge of the frame.)
Normally, the bottom side data will be mirrored so that the bottom side of the stencil will be in contact with the board, regardless of which side of the board will have solder paste applied. This may be disabled by unmarking the Mirror bottom data check box. You may also choose between horizontal and vertical mirroring.